What if bottom gets prego, but since his body isn’t supposed to, it taken a toll of his life while giving birth. So the Top regrets it. The child survived but became a very own reflection of Top’s mistakes, so Top neglects the child. But the Scientist raised the child as some kind of test subject.
Then the 2nd ML adopts the child because he reminds him of the bottom.

It’s already fcked up so whynot go further :P