I'm really at a loss with this, and have been for two decades.
When you see friends, family, or even pets, it is supposed to trigger recognition, and that recognition is supposed to trigger an emotional response. This happens even if it's only photos or video you're seeing. I experience the recognition part, but it feels like the emotional response that gets triggered is only a 1 or 2, if it happens at all.
When one of my friends died in a car accident I didn't feel any way about it. My other friends and I were trying to find out what happened to her, what hospital she was taken to, but to me it was like a puzzle to be solved. I wasn't worried about her, afraid, sad... nothing. When we spoke with a police officer and he said he needed to tell the family before he told us, I knew that meant she had died, yet it entered my mind like mere information. It didn't make me feel anything.
The same thing happened when my Grandmother was dying. She had been a fantastic grandparent to my sister and I. Very good to both of us, never did anything to harm us, and even lived with us for a couple years. Yet when she was dying there was nothing... even years later I still haven't ever felt any way about it. In fact, as disgusting as it sounds, near the end I remember wishing it would just hurry up and happen because it was disrupting normal everyday life for everyone.
It's not just around death though. One of my neighbours used to invite me over to watch movies. He was an older guy whose children had grown up and moved out of the country, so I think he and his wife were lonely. I didn't mind going over because the movies were ones I had been wanting to see. However, before and after the movies he would want to talk, and one time in particular he shared a really personal story about himself and began getting emotional. Rather than a normal person's empathetic response, what went through my mind at that moment was
"Wow, he really trusts me. How can I use that?"
The thought surprised me with how blunt it was, but I wasn't surprised at all by the lack of empathy. When I see people crying, even if it's people who I
should be close to (like a parent or friend) I don't experience the desire to console them. Instead, it's like I'm irritated or put off by it and lose respect for them. I know that's not what you're supposed to feel.
None of this is to say that I never experience emotion though. I still get happy, mad, or feel down at times. It just seems like I can't feel anything when it comes to others

If that makes sense.
Much of my childhood is blocked out so I can't really say for sure if it's always been this way, but I know that I had always treated my friends as though they were disposable. The lack of empathy certainly became more apparent when I was around 12... though perhaps I just began noticing it more, because that was the age you're supposed to start being interested in relationships. Twelve was the age when the abuse I was going through became much worse, so I don't know if this is really who I am, or if it's PTSD from that abuse. Or it could even have been caused by a surgery I had at that same age. During the surgery the blood to my brain was accidentally blocked off for a brief period, and the surgeon was sweating about it when I came to.
But does what I described sound like anyone else?
If so, do you know why you are that way?
When I think about it I feel like I'm an alien stranded around a species that experiences life differently from me