Is it normal that i have an extreme lack of empathy?

My lack of empathy is not just tward strangers or even friends but also close family members. I dont mean an aunt or cousin either, im talking about my parents and siblings who i practicaly helped raise. And also by lack of epathy i dont mean your average i jst dont care or dont want to care, Im talking about complete apathy in seemingly traumatic situations.
One of the most concerning situations was a few years ago when my younger sister had a serious asthma attack right after running out of her medication and i was baby sitting. After talking to my mom about whether or not to call an ambulance I went to check on her and my youngest sister. She was sitting on the couch crying and gasping for air and my youngest sister was sitting beside her hugging her and crying also. Confused, I walked over to them and asked the youngest why she was crying and she said "Im crying 'cause i want her to get better and i dont want her to go to the hospital again, and I want her to be able to breath", And I was completelybaffled. The whole time this had been happening I had not once stopped to think about think about the fact that she was in pain. I was more concerned about how much of an inconvenience this was for me, and now seeing them like this i felt absolutly nothing, like, void of all feeling. And whats worse, seeing them crying together and me feeling absolutly nothing I felt out of place, and kind of like an intruder. I just stood there awkwardly staring at them with no clue what to do or how to comfort them. At that moment i realised that the reason i never showed compasion for them wasnt just that I was mean or evil (as they and my mother had so often put it) but that i cant. I felt so distant from them and everyone else for that matter. It was just like there was something there that I just couldnt quite get. There were alot of other instances like this but this one was the most revealing. Has anone else ever gone through similar situations, or thought like this? Should I seek proffessional help, or is this normal.