I NEED BRUTAL HONEST ANSWERS! BUT DONT BE RUDE😘

Ok so I’m having an issue and I’m not sure who to have it with. I’ve been dating the father of my unborn child since September of 2016. Apparently his ex girlfriend is friends with his sister and there sons have play dates a lot. Now that’s all fine. I’ve been coming around for his family holiday gatherings, birthday dinners, also bringing my other four children into the picture. Now all of a sudden she (his sister) is inviting her (the ex) to family functions. Last night his mom had a birthday dinner and personally invited me. His sister is the one who put it together and personally invited the ex. So I didn’t attend. But he did. Which is fine that’s his mother. This really hurts my feelings tho bc I have had bad encounters with her (the ex) on more than one occasion since we’ve been together and I feel no one is considering how I feel about it. It makes me uncomfortable. I know If it was me I wouldn’t be inviting my brothers girlfriend to our family functions knowing he has moved on. I feel like he should speak up about it but the fact that he doesn’t really raises concerns for me. Play dates are one thing but to me this is too much. It makes me not want to have a relationship with his sister and they are really close. Am I over reacting? Is this pregnancy hormones? Should I even care? Please give me honest answers. What should I do?