The Tringhams do not appear in the FMA manga, but they are minor characters in the anime and the plot of the FMA book The Land of Sand is centered around them.
...The book is weird and I don't actually recomend it unless you want something to draw Tringham family background from. Hell, the book's official translation disagrees with itself on how their last name should be spelled, and in the book Al is apparently made out of bronze. But family background is always nice for roleplaying.
And, of course, some time this winter it provided material used in CFUD about how Russel is just a horrible, abusive brother.
This is the scene, followed by the one right after because it works towards my point of Russel not being abusive, and because it helps explain the Tringham fear of the military just a little:
---
With a wave of Fletcher's hand, the door disappeared, leaving the wall in its original state. He turned to his brother, his eyes fixed on his feet. "I'm sorry."
Russel's face was set in his usual mask, but he was furious. Yet when he spoke, his voice remained cool and even. "You mean you're sorry you let them go? No need to apologize. It's a good thing they didn't get caught and tell Mugear who they were. Then we'd be in real trouble, huh?"
"I'm not talking about that."
And you know it, but you're too mad to even say it.
Fletcher swallowed. "I'm sorry I used alchemy."
His brother's eyes burned into his, and Fletcher had to turn his face aside. He had promised...
Russell sighed deeply and turned away. "What would Father think? He asked us never to use alchemy. We promised! I...I hoped that you, at least, would keep that promise."
Fletcher stared at his brother's back. Come to think of it, in a number of ways, he felt he hadn't look straight into his brother's eyes since their arrival at the lab. He couldn't bear to.
I don't want to see you lie.
I don't want to see you using the Stone...using alchemy.
I don't want to see you drown in your research...
But it seemed to Fletcher that he could see chains around his brother, chains binding his thoughts and his actions. They were wrapped so tightly Russell could barely breathe--yet he couldn't see them. All this time Fletcher had thought he was the one who was trapped, forced to go along with his brother's lies, but now he could see it was the other way around. Russell was bound; Fletcher was free, and only Fletcher could see the truth. But how could Russell be freed?
He was lying to make someone else's dreams come true.
He was devoting his life to research to finish what someone else could not. He was using alchemy, all the while apologizing for it to that someone else.
"Can't you see?" Fletcher whispered.
"See what?"
Why did we lie and say we were the Elric brothers?"
"We had to so we could do our research here."
"And why are we doing this research?"
"Because it's what he wanted. He wanted to redeem this town."
"If you think that's what he wanted you to do, why don't you just use your own alchemy instead of those Stones?"
"Because he told me not to."
Russell can't see the chains...
"Does it make you happy, doing all this for him?"
"I'm doing the right thing."
The chains are so heavy.
If that's true," Fletcher shouted, his voice trembling, "why do you look so miserable!?"
Fletcher was filled with pity for his brother. It was time to give a name to those chains. "You're not our father!"
Russell's face haredened.
"Our father was a great man," Fletcher continued, "and a talented alchemist. We started doing alchemy because we wanted to be like him, remember? But when he told us to stop, we did." Fletcher's voice choked. His entire body was trembling, and he was on the verge of tears. "You told me it was all right to lie to get into this lab so we could carry on what our father started. But you're pushing yourself too far with those Stones--and for what? For who? You're just following the same path that he walked! Why, Russell? What about what you want?"
Russell said nothing.
"Our father had the talent--he even made apprentice to a State Alchemist. But then he quit and came to do research here. He had his reasons, I'm sure, but all the same, he didn't want you to follow in his footsteps. Russ, if you keep on like this, you'll kill yourself..."
The two brothers had dreamed of becoming alchemists, just like the one they most looked up to, their father. But he had ordered them to give up their dream. It would have been hard on anyone.
"You think Father would be angry at me for using alchemy like I did just now? How do you think he'd feel about us stealing the Elrics' names? I used alchemy to help them, and if I can use my talent to help others, then I'll keep on using it. In fact, someday, I want to be an alchemist."
Russel stared at Fletcher. Fletcher cringed. Would he shout at him? Would he punch him? He'd done both. But Fletcher wouldn't turn away. His brother was wrapped in chains he couldn't see, and it was Fletcher's responsibility to set him free. He returned Russell's gaze, and his heart filled with courage. This was what Alphonse had given him at the pharmacy. It was a fair trade.
--
In the End, Russell said and did nothing. He just turned away. And then a guard appeared and told them to report to the main hall. Without a word, Russell began walking back toward the mansion.
"Russ...?" Fletcher followed, watching his brother out of the corner of his eye.
Russell's face was white in the moonlight, an emotionless mask. Suddenly their positions had reversed. Now it was Russell who couldn't talk, Russell who had been silenced by Fletcher's words.
As they entered the hall, they saw Mugear halfway up the staircase to the second floor, leaning on the banister. He was looking over some documents. He glanced over at Russell and Fletcher when they entered.
"So you drove off the bandits?"
Russell nodded. "Yes."
"That's two nights in a row. This is beginning to disturb my rest. You tell me we should merely drive them off, Master Edward, but perhaps it would be better to capture them?"
"No. They can perform a little alchemy. If we brought them inside, who knows what havoc they might wreak? If we keep driving them off, they'll give up eventually." Russell spoke quickly and without hesitation.
Mugear shook his head. "No, I think not. I believe you're worried that I'll meet them and your deception will be revealed."
Russell tensed. Beside him, Fletcher gasped.
"You instructed me to take shelter in the cellar, so I did, but I had so much time on my hands down there...Plenty of time to think things over."
Mugear came down the stars, sliding his hand down the railing. "The cellar of this house was made for holding people who wouldn't listen to reason, you see. I was just thinkg about the last person I put in there."
Russell swallowed and said nothing.
"He was a man from this town, in fact. He left years before to study alchemy at the capital. He had great talent, but for some reason, he returned despite having just begun his apprenticeship. I'm not sure of the details of his departure, but he seemed very frightened. I offered him safe haven, and in exchange, he agreed to make me a Philosopher's Stone. He said he was through with alchemy, but when he saw how shabby his hometown had become, he agreed to do research for me, as long as I permitted him to continue his work on the Water of Life. He said the Water would help restore the greenery that this town had lost so long ago.
"My intentions were noble. If he had completed the Philosopher's Stone, I would have used my influence to make certain the military didn't come after him, and I allowed him to do as much of his own research as he liked. I was generous, too. I gave him all the materials he requested. However, all he did was repeat the same experiments over and over, to no purpose. He would not listen to reason, so I put him down in the cellar or a while to think things over."
Mugear held Russell and Fletcher in his steady gaze as he spoke. "I remember he told me he had two sons. Brothers with golden hair and silver eyes. He would smile as he told me how they resembled their late mother. When he completed the Philsopher's Stone, he said, he would say adieu to his life of toil and summon his sons to him to share in the paradise of Xenotime. His name was...ah, yes, Nash Tringum, I believe."
Mugear threw down the documents he was holding. They drifted to rest at Russell's feet. The documents identified State Alchemist Edward Elric.
"Apparently the real Edward has gold hair and golden eyes." Mugear strode over, grabbed Russell's chin, and lifted it up. "your eyes don't look gold to me." He swung his fist back and hit Russell hard on the jaw. Russell fell to the floor.
"You're Nash's sons, aren't you!?" Mugear snarled.
Russell just ast on the floor without lifting a hand to defend himself and said nothing.
"The ones who came here--these bandits of yours--I know they're the real Elric brothers. I'll bring them here and have them prove it." He grabbed Russell by the lapels. But Russell's face remained a mask, as always. Mugear rasined his fist again and hissed, "Insolent child!"
The fist fell on Fletcher, who leapt between Mugear and his brother.
"Please, stop!" begged Fletcher. His head began to pound. "It's just as you say. I'm Fletcher! And this is my brother, Russell. Nash Tringum was our father!"
"Fletcher!" Russell pulled his brother to him, and saw the bruise forming on his forehead. He shot Mugear a furious look, but by then, they were surrounded by guards.
"Throw them in the cellar!" Mugear ordered. The guards pinned Russell's arms behind him and shoved him towards the stars leading downward.
"Oh," Mugear said with a smile. I almost forgot." Reaching into Russell's pocket, he pulled out a faintly glowing red shard. "I see you've gotten some use out of your trial Stones. You might even be able to make a little gold, no?"
Mugear grabbed a candle and studied the reflections in the Stone. For a moment, he was lost in fascination as he gazed upon the shimmering light. "I'll have to summon new alchemists to complete my project, and I'll have to raise more money to fund their research. Things will be hectic around here."
He cared nothing for the townspeople, whose lives would only grow harder as he continued to bleed them to fund his project. Mugear's only interest was the obscene wealth he dreamed of acquiring for himself with a true Philosopher's Stone.
[/chapter]
Now, I would like to present the line in particular that makes people think Russel's abusive.
Russel stared at Fletcher. Fletcher cringed. Would he shout at him? Would he punch him? He'd done both.
...Russel has canonly shouted and punched Fletcher sometime in the past. Yes, okay? He did. I submit, however, that this does not make Russel abusive. "Why, Russel, why do you say that?"
Because family fights. Give me one example of siblings who haven't fought. Hell, Ed and Al fight in both the anime and the manga. Let's review the situation: Russel has just tried to kill Edward, who is at this point, decidedly his enemy. Edward has declared that Russel's work, currently one of the most important things in Russell's mind, has failed and that Russel will have to give up on it. Russel knows that his research isn't working. Russel is already about as angry as he ever gets, and in book canon, Russel has incredible control over himself. On top of it all, Fletcher's breaking promises, and ripping apart Russel's careful justifications of all the bad things he's doing. Fletcher just started shouting at Russel about incredibly sensitive matters. He basically just CONFRONTED Russel with the things that Russel is refusing to see--the "chains."
If you're a timid person like Fletcher, you'd probably be afraid of being hit in that situation, too.
I suppose that this isn't entirely conclusive, but. In addition to that, Russel considers family another of the most important things. He takes incredible care to make sure Fletcher is not harmed, and when Fletcher is hurt, he's about ready to flip out and choke a bitch. In one of the first scenes of the book involving both brothers, they're fixing equipment for the locals, and Fletcher takes a chisel to try fixing it with alchemy, but Russel immediately gets it away from him and lectures him out of fear that handling the equipment, Fletcher will get hurt.
Russel won't let Fletcher touch chisels out of the fear of Fletcher being hurt. With all of this in mind, I submit to you, the reader, that Russel Tringham is not abusive. At the most, I think that one could argue that Russel may have been abusive sometime in the past, but I find this just as unlikely. I honestly think it's just from a past fight that they had.