Really it depends if your a momma's boy/girl or a dadda's boy/girl. It will also differ on what you are doing right now w/ them. The Pros and Cons about both help decide, too! It's just the type of person you are.
Your step dad had an emotional affair and your mom is devastated how can you help her get through it?
show your mom your there for her and let her know theres more to life and theres someone out there better than him. and tell her theres no one that'll be there for her better than you.