I.e. Humans can sometimes meet even their great-great-grandparents, but are there any species that can be alive at the same time as their great-great-……-great-grandparents? I imagine it would be those species with a long lifespan and an early age of first reproduction.
Yes, cryopreservation works quite well for many species, including multicellular animals. So you can freeze the ancestor and wait until the descendant is there, then unfreeze them. A good recent example in the news would be the Siberian worms that woke up after being frozen in permafrost for a very long time.
Cryopreservation is routine in laboratories, to freeze ancestors and compare to descendants; see the Long Term Evolution Experiment. It doesn't work well for every organism of course. In principle it might work for humans.
Some bacteria will sporulate, and in spore form they can persist for thousands of years theoretically. They don't even need cryopreservation. There are other organisms that do something similar as well.