Morning Maddhouse: We Family Wednesday (6/13)

My parents were never married and can't stand each other.  I have always lived with my mom & she never kept me away from my dad.  We have always had a good relationship.  He is married & has a step daughter that's the same age as me.  He's been raising her since she was 3 years old.  I don't have a relationship with his wife or step daughter.  They aren't nice to me or my mom.  Recently I graduated from high school on the same day as his step daughter.  Instead of attending my graduation, he went to hers.  When I asked him why didn't he come to my graduation, he said he knew my mom's boyfriend would be at my graduation but no one would be at hers other than her mom if he went to mine.  I am so hurt.  I am his blood.  What should I do about my dad?