I dunno, but if either lot of your kids haven't produced Grandkids
yet, and you've actually got those 50 years of riding experience you told us you had in an earlier post (and I've no reason or suspicion at all to think that you don't!

) then unless, like me, you married someone a fair bit younger'n yourself (hence my Wife's much bandied about nickname, 'The Child Bride'!

) surely your kids are at least pushing if not past the age where grandkids are becoming somewhat unlikely, if not bloody impossible without a miracle; lotsa drugs & IVF type intervention; &/or maybe fostering/adoption?
As
you say tho, Cats, Dogs, other pets, even young Saltie's (don't laugh, I know a couple of couples who have one now!

)
can fill the void in your life that not having Grandkids & Great Grandkids can leave, even if you don't realise it's actually there!
Or like
I said, there's always Fostering or Adopting - it's wasn't a formal thing with us (altho a few have since been formally 'recognosed'...), but me'n the Child Bride have picked up a few 'Surrogate' Kids, Grandkids, and Great Grandkids along the way, and when the whole lot can make it at the same time (which they often
DO! 
) our family gatherings are pretty large and quite noisy affairs. But they all get along with and actually
LIKE each other too (plus, they put up with me, even seem to enjoy having me around... sometimes!

), and all of them would never turn away a Kid in need, so the 'Mob' just keeps on growing!