My List includes mangas where the children are theirs and not theirs. There are also no-yaoi mixed in.
http://www.mangago.me/home/mangalist/27443/
Just in case youre searching for yaois:
http://www.mangago.me/read-manga/futari_no_musuko_ni_nerawarete_imasu/
http://www.mangago.me/read-manga/papa_i_love_you/
thanks it was helpful
Does anyone know any yaoi manga's where the main characters have to watch children that aren't theirs.