Dad died

My mom just called me to tell me my biological dad died. We weren't close. He was never involved in my life at all. In fact I remember meeting him like three times in my life. I feel like I should be sad, but I'm not. I mean sure he was biologically family but I'm more sad about a mother loosing her child, no matter how awful that women or that child is, its sad to me. I don't know. Has anyone been through something like this before?