I starting to hate the fact that the author made him very clumsy. At least tone it down a little. He can improve when he tries so have him improve at least a little bit.
He wants to stay a family??? By getting adopted? Because unless you get adopted you have very few options to making that real. It’s not even legal in Japan to have sisters married in poly relationships
It's probably not them, but the yankee dude and short-haired girl at the batting cage (page 5) reminds me of that 1 manga with the helpful yankee that seems to have the most random but appropriate tips to give to everyone. The title was Tourigakari ni Wanpointo Adobaisu Shite Iku Taipu no Yankii.