Responses
Yep. I get that they're instrumental to the story (kinda) leading the plot to progress further (investigating the truth, leading brothers to reunite, causing them to realize their feelings, etc.) But if I met those two in real life and they just started hanging around my house after barging in and causing trouble, I'm going to make up my mind and drive them away.
Honestly, the kids annoy me, but if I look at it from MC's POV, they might have made his life less lonely. And even though we see them every chapter, they only go see him on the weekend, so he's probably left alone with Mitsuki a lot.
There were so many interesting backstories going on. Would be nicer to know more about them like other comments have pointed out.