Moms boyfriend...

So basically my mom has a boyfriend and they’ve been together for a while now. Anyways he lives in a different province so he comes once every couple of months. Anyways when ever he comes he doesn’t try to spend time with us, he just keeps my mom to himself. To make matters worse he planned a vacation around my siblings and I. He invited my mom to meet his family and his nieces and nephews without us in the Dominican Republic. He didn’t even bother to include us and my mom fails to acknowledge this. Another thing is he keeps pronouncing my name wrong and my mom corrected him and he said “ I’ll pronounce words the way I want to say it” and all my mom did was laugh. He still continues to say my name wrong not because he can’t say it but because he chooses to say it wrong. What are your thought on the situation, I’m just wondering because I don’t want to seem like a brat when I talk to my mom about this. And how should I bring it up to her ?