Asking about Parent-Child relationship karma. Is it bad if I don't wanna go visit my dad? My parent seperated since I was young and I was rise by my mom.
Right now my dad is not in a good condition and unfortunately my aunt and uncle from my dad's side doesn't like me much. Too be honest I don't wanna face with my aunt. I know she loves him so much and she hates me because I choose to stay with my mom. I don't know what to do. 

For example today I told my mom I will go visit my dad but mom said she needs me to have a dinner with her.so she told me to go visit my dad the other day... 

If I don't go visit him.. Will it be bad ? 

I know this is such a stupid question but it is hard for me to make up my mind. When I see my dad It is not so peaceful inside because of the people around him...
Your question is very important, but difficult to answer, since within Buddhism answers are not always what we want to hear.
Your father and his family members are experiencing there own karma, which in this case is not good for them or pleasant for others.
Within yourself you should try to find loving-kindness for their suffering. You can accomplish this by realizing that the bad manner that they use with you is a lesson in how not to behave. Try to find compassion. This will help your mind to accept, and realize that your visit with them is temporary...when it is over do not dwell on it.
In Tibetan buddhism all sentient beings were once our kind and loving mothers. We try to remember that in our dealings with others. It is not always easy, but you will be a better person if you have compassion for all others.