What does Como se llaman tus padres mean?
Meaning- What are your parent's names
Literal - How are your parents called.
This asks, "What do your parents call themselves" or "What are your parent's names" so you would say "They are named Bob and Susie" or whatever their names are. In Spanish this would be: "Se llaman Bob y Susie" or "Mis padres se llaman Bob y Susie." The subject tends to be optional in Spanish, especially when the listener already knows who you are talking about.