Tenjou no Shita ni Koi
Guy moves into a house of 4 brothers just struggling to be a family and everything is thrown out of wack for the better. They all, minus the youngest who is super little, hit on him or seem to have a crush on him at some point lol. I enjoyed this. Would've given it 5 stars if the translation wasn't so, well........ not good at times.
Anitsuu!
College boy suddenly gains 3 little brothers when his dad remarried. He slowly, one-by-one wins them over with his good intentions and desire to make them happy. Of course, all the boys fall for him to some degree. Cute and sweet!
Bokura To Usagi No Koi Wa Sensou