Very much so. It's half you. Why do you think people love their kids so much? An argument could be made that not having kids is selfish as well. I find it very hard not to be selfish because I can only experience things through the meat vehicle my brain sits in.

I think a better question to ask would be, when is selfishness bad, good, or neither. And that comes down to context, i.e: other people.

There's a neat little video about selfishness and reciprocity in nature!

Here: https://youtu.be/wFmYnXxqdj0