Need Advice!!

I don’t even know how to start but here it goes. So my Boyfriend and I have been dating for a year now. But he hasn’t “officially” presented me to his family. He has 2 kids from a previous relationship and I have 2 kids of my own also. So what I need advice is that I’ve only met his kids twice and every time I invite him to hang out with myself and my kids he always says well I have to ask my kids if they want to. I feel like he doesn’t want me to hang around with his kids. I want to get to know his kids more and see how well they react around me. I don’t know how to bring this up to him. Plus we went on a mini vacation 2 months ago and his daughter wouldn’t even let me sit next to him and she would say things like don’t hug my dad or you can’t sit next to him . I didn’t say anything because I didn’t want him to think I was overreacting. But both times we hung out she did the same thing.