As others have pointed out, this is messed up.

Seriously? I can't even begin to dissect the levels of fucked up this is. Planning a trip without him, commandeering his family, making him feel like he's less important to his family than you, making him feel his family is more important to you than him, making him feel like an afterthought.

Not to mention, what's happening if you guys break up? Is he going to have to keep you in his life while you're bringing new guys to HIS family functions? Are you planning on isolating him from his family and just stealing it?

Yeah, it's all types of fucked up. You are so kind to invite him to stay with HIS cousin at HIS grandparents. That is so fucked up.