Most Helpful Guy
That does seem to be a strange situation. However, your mom is an adult too.
If your mom is fine with it and likes talking to him, then that is her business. Are they like... friends? They could be friends...
If they're NOT friends, and she is just being polite by answering the phone or ingratiating his questions, then yes its really sick.
If they ARE friends though, it would explain a lot. They might just have a lot in common or cool things to talk about.