Odd request. I have not read or heard of this fic, but everything I know about fandom tells me it must exist. So here's the plot:
Steve is Tony's biological father, with Howard as the other parent. Most likely scenario, Howard, after decades of not finding Steve, decided he would at least make sure Captain America had a living legacy. Howard thus assembled (Ha!) him a son using - let say 'Captain materials' - in cold storage. Neither Tony nor Steve know this of course (but Fury might).
So does this exist (and preferably NOT as a Greek tragedy)?
ETA: Really!? Nothing? Bueller? I guess it doesn't exist... Yet. To the Kink Meme!