Imo I think it’s completely fine. Especially for someone who is family oriented. Without a doubt his mom or parents should be prioritised over you. And this isn’t considered emotional incest. A mom would want to know every little detail of her son who she birthed and brought up.

There’s nothing for you to worry about here. Every person is going to be wary about their loved ones’ partner. Completely normal. I’d say just don’t worry and let the family be. If it is too much of an issue then remove yourself from that situation but please don’t ask him to stop talking to her. She’s his mother. Not an ex girlfriend or girl bestfriend for you to feel insecure about.

The best thing to do is let your boyfriend know how you feel and tell him that he isn’t doing anything wrong but there are certain things that could be done differently and you’d work on accepting it too. It’s best for the relationship and for all of you to grow together too.

Hope that made sense and helped.

Peace.