22 and 18 with a 76yo father

The thought of our dads mortality has been creeping up on my sibling and I now and with each death I see in the news of people from his generation, the more anxious I get. We still live with him and generally depend on him, and he's in fairly good health and is pretty active which is good, but hell, parents in their late 70s isnt something either of us should be having so young. Most people are out on their own or have their own families by that point. You think of your future and you imagine your parents will be there for at least a decent amount of time before they go. And I know that statistically, the older you are the longer youll live, but...well. I dont know if even the next 10 years are likely. In 10 years Id still want to have my parents to refer to for advice and all that. I mean we still have our mom whos much younger, but she isnt the most reliable. We cant like go ask her for help on random bureaucratic crap like we can with our father, who is not only more experienced but an ex-govt worker. Ive already discussed with my sibling that its pointless to bring up to him the age at which he had us and how irresponsible it was since it cant be undone, but the financial situation is tight, and compared to our adult half siblings, its like we got the leftovers. And dads aging just makes it feel like he promised all these things, support, being there, "dont worry about it", but when he goes he wont have to deal with the aftermath. He doesnt have to deal with the anxiety. I dont know who to really talk to about this bc our situation is so niche and we get weird reactions to people seeing us and then reconciling our youth with dads age (and yes, it was a weird origin with all that it implies). people our age arent worrying about this sort of thing. like, being a parent is a lifetime commitment. and while i understand we dont live forever, i wouldve, idk, at least wanted my future kid to have a grandfather? as weird as my dad was he still gave me plenty i value, not like in physical items but in experiences/knowledge. and i just hoped id be able to keep in touch with that for longer.