What do you do if a child loves their step-parent more than their biological parents?
Sometimes it is easier to talk with someone who isn't your mother. On the face of it, it doesn't sound that bad, because at least he is comfortable talking with an adult in the family. I don't confide in either of my parents, so he's doing better than me. Part of the reason I don't confide in my mother more, is because she is hypersensitive to things. She is too intense. I'm guessing it has less to do with what/where the son is, and more with how the mom tends to react to things. Imagine those people you don't confide in, and ask yourself why you don't.
I missed the part about where a problem exists. If the bio mom feels left out, she needs to make a stronger effort with her child. This is actually not uncommon because the step parent presents themselves as a friend, not a parent.
the bio parent needs to become better obviously