AU Bilbo/Thorin Innocence Kink (FOUND)
Looking for a fic from AO3. Pairing was Bilbo/Thorin (M/M). It was an AU where there was no Ring & no Smaug. Thorin was king and was married to Dís (who was not his sister in the fic). Dís didn't care much for sex so she suggests that Thorin take a second spouse. Thorin eventually agrees and Dís get princes and princesses from all around to come to Erebor and she decides that Bilbo will be perfect for Thorin because Thorin has a secret kink for innocence. And Bilbo is completely innocent having been way over sheltered by his parents growing up.
Bofur is elected to keep Bilbo and Thorin from meeting until Dís decides that Bilbo is the right choice. But Thorin gets Bofur to sneak him in to see Bilbo. There is slight dub con because Bilbo is so innocent that Thorin convinces him a hand job is a"royal handshake." There was some frottage as well if I remember.
I think it had hints of Fili/Legolas in it as well and I know that Frodo was Bilbo & Thorin's child and eventually Frodo married Aragorn at the end.