Can someone tell me a yaoi manga where the seme is the one who already has a child and the...

http://www.mangago.zone/read-manga/koishite_daddy/
the uke isn't really a babysitter though, he's the neighbor.

http://www.mangago.zone/read-manga/gochisousama/

http://www.mangago.zone/read-manga/tone/

http://www.mangago.zone/read-manga/yokubou_shounen/mrs/manga/yokubou-shounen/v-1/5/

http://www.mangago.zone/read-manga/papa_is_a_bride/ (don't know who seme is yet)

http://www.mangago.zone/read-manga/everyday_smile/