Just a single bunny really ^^;
Ratchet once long ago had a sparkling (whether it be with Ironhide, Wheeljack, or even a mech he had an one neighter with. All depends on how you want to look at it.) and not a day has gone by that he regretted his decision in doing so just because he was convinced that he wouldn't be able to take care of the sparkling so early in his career. Even with the help of his mate (( this part is only if writer went with the sparkling being Ironhide's or Wheeljack. ))
Now many year's later Optimus has hired his crew to attend him on the ARK, and all mechs are required to go through a full check up. While working with Red Alert, he notices that the Lambo's spark signature is VERY similar to his own, and he instantly realizes just who Red Alert is. His sparkling, which is the main reason why he seems so spent on trying to cure Red Alert's glitch through out the time he was on the ark.
Ratchet has always thought about telling Red Alert that he was his creator, though after it is revealed just how hard a life Red Alert went through (where he says it on accident while under the influence of a pain medication, or even from a file) and learned that he blamed his true creators for it all. Which of course stopped Ratchet from revealing who he truly was to Red Alert.
So many more years later, some how whether it be by Red Alert over hearing a conversation ratchet is having with someone, or some other means. Red Alert learns the truth. How will he reacted when the medic who has treated him for so many years was the very same bot who sparked him and abandon him as a sparkling. .