Dwayne writes
Hi. I have never tried to start them inside, but I would think they need
some cold hours before they will sprout, almost everything else does.

Only things which naturally grow in a climate where there is a cold
period!

I wouldn't have thought this applied to peaches, but what would be
helpful would be getting inside the stones. This is probably why Dwayne
finds they come up in spring - it may not be the cold per se, but the
fact that the stones break open during the winter, allowing water to
penetrate to the seed inside.
--
Kay