What should I do about my dad?

My mom and dad have been divorced for 13 years. My brother is 18 and in High School and Im 20 and I work and go to college. Recently my dad married this woman and didnt even tell us. We had to find out thro the newspaper. This woman has 3 kids. Her oldest son (who lives with them) he is 24 ( he is mentally insane for sniffing battery acid), and another son who is in prison for 8 years, she also has a daughter who lives with them and she is 19 and she is in college. Ever since my dad and his new wife got married he hardly has anything to do with his kids. My brother lives with my dads mom and they live about 10 mins from my dad. My brother sees my dad about once every 2 to 3 weeks. I live 4 hours away from him. I came up to see the family one weekend and my dad made an excuse about comming to see me. Later I found out that he was 5 mins up the road from me. He texts me every now and then and when I text back I get no answer. He says its bec his battery is dead or that he left his phone in his truck. This last christmas my dad didnt get me or by brother anything but he got my step sister a 500 dollar phone. Well now my dad just got out of the hospital and I went to see him but He always brings her along, if he dont she pitches a fit and they get into fights. I want to have something to do with my dad but I cant when she is around, its like she is his boss. Whatever she says he does. I want to have a father-daughter relationship with him bc Ive never had one. Is it to late or does he not care? What should I do?