Akarui Kazoku Keikaku ("Cheerful Family Plan") by Arata Yoshikawa 10 volumes-complete
Honoka moves to her aunt' s home full of boys. The catch is that her aunt is not physically at her home. There's a blurb (I'm not sure if it's from the mangaka or scanlator) that says to the effect of being oblivious that they're cousins and all. Well we wouldn't know if they're really cousins or not since her aunt is still not around on the 4th chapter. There's also kindergarten twins! I'll probably just add them on the total result of the running polls as special mention or something.
Thanks to Michelle for the tip!