Question about my fiancee's mom...?

Don't get me wrong, I like her a lot, she's a really sweet lady. I just wonder though, she calls him a lot (lately, its every couple of days). He's 28 years old and we live together. Is it normal for a mom of a man that old, to be calling and emailing him so often? He has another brother who's wife kind of curbed the mom calling him so much, and now I think she's turned to her oldest son (my fiancee). I speak to my mom about once every couple of weeks (we live 5000 kms apart), and he speaks to his mom and/or sees her and emails her OFTEN every week, and they live about 50 kms apart. Just wondering if this is a little too close or is this normal? It just seems kind of excessive to me. I'm a little worried he's becoming a mamma's boy:-(