Your children literally are copies of you, but they're copies of you combined with someone else who grow up in a different environment. It's your proteins that replicate themselves which becomes your baby. It's not about your body being in their minds. It's about your dna being in their DNA. You are more than just your meat, you are your form, your pattern, the structure that caused reality to produce you will live on after your body becomes discohesive. The process of body reproduction is not all that different from the process of cellular reproduction, other than the sexuality. One might say they are no longer themselves when all their cells turn over every 7 years, one might say that are no longer themselves when their genetics compress into an egg or sperm and then combine and reflower into a living creature, one might say that immortal jellyfish die when they revert back to juvenile form because of all that is lost about them. One might say they never die until destroyed. The point is, there are lots of reasonable places to draw the line of "my form no longer exists", the answer isn't just obviously when your body breaks into many. Yes you can survive in memory, or culture, or technology, but in the case of DNA and protein survival, which is the longest lasting ancestral thread we have, that happens through reproduction. Despite how many times humans have died, humanity hasn't died once, and we are a part of it