This is an interesting thread, I've been having a bit of an existential crisis around this subject.
I'm an only child, and have one DS. He's in his 30s but for various reasons it's unlikely he and his current long term DP will have children. His F vanished when he was a toddler, and has been no contact, although I did find out DS probably has a half sibling, however, there's been no desire on either side to pursue a relationship.
I'm in my late 50s. Obviously my GPs are long gone, and in the last 5 years I've lost both parents and my last Uncle on my DFs side. I have 2 cousins on that side of a similar age, both of whom are childless.
Family estrangement dating back 30 years means although three cousins from my Mums side have children, we are not in contact.
I am now the oldest female in the family, but due to the awkward dynamics and various other factors, senior matriarch is a nominal role only.
Our only "family" gatherings are now funerals.
On the one hand, it is what it is and I'm pragmatic for the most part, but it's odd to realise our family history, such as it is, will die with my DS, and is somewhat in its death throes now.
It's oddly maudlin making, but just the way the cards have fallen. Effectively, my whole line will have ceased to exist in another 60 years or so......