Feeling sad

So my boyfriend and I have been together for about a year now. I really want him to meet my kids. I have twins that will be 10 in May. I’ve expressed this to him many times and I feel as if he puts no effort into even attempting to meet them. I’ve brought it up many times and he says he’s down to meet them but then every time there’s an opportunity to meet them or I mention it…the conversation fizzles out and he almost avoids it. I am not going to force him to meet them so I just drop the subject…but it’s really starting to hurt me and make me feel bad.
He also hasn’t met my family and I haven’t met his. He tells me it’s because we’re in a poly relationship and he doesn’t want his parents to know. His other girlfriend is with him for every family get together and holiday and I’m just on the sidelines. It makes me want to cry. It hurts me a lot. It makes me feel like I’m not important. I ask myself is this even a relationship? It doesn’t feel like it sometimes. It hurts me a lot. I love him and I don’t mind being poly. I don’t mind him having another girlfriend. What hurts me is that feeling of not being included. Being left out. That he’s hiding me. That he’s ashamed of me. That he doesn’t value our relationship enough to do any of the things I mentioned. It hurts me a lot. And rn I’m really struggling with it.