Who's the first person you want to share good/bad news with?

I am in a very serious/committed relationship with my significant other. We have both graduated from college years ago and are adults. Despite all of this, he doesn't understand why I get upset/hurt when he goes to his mom first to share good/bad news. I totally understand him wanting to maintain a relationship with her, and I don't discourage that at all. However, I think at our age, and with the seriousness of the relationship, he should come to me first and then talk to his mom. I always thought there was something special about the person you can't wait to share your news with. Am I wrong? What do you guys think?