There are many relationships where one party is the adult and the other one is the child. That dynamic is not specific to A's. It is a dynamic that evolves over time if you let it.
Your AH probably didn't just start wanting you to help him, right? If you have historically done things for him, then that is what he is used to. You both created that dynamic. Are you just noticing now?
If either of you changes, then the dynamic changes.