I'm going to defend my son who cheated on his girlfriend against my daughter
What do you mean by cheating against your daughter?
I don't want my son getting degraded for what he had done and I hate people that run their mouths off about him.
It is normal to want to defend your kids from people attacking them but it is not good to support their actions when they are bad. He cheated and does not need to be protected from his actions.
Well, he is my son. And if he thought cheating was the right thing to do, then I should wholly support him for doing that.
I understand your love for your son, but you are insinuating it can possibly be incestuous which is wrong in itself as well. I think it's best that the three of you try out counseling to sort out the deep issues.