I came very close to seeing this happen for myself, so I've still not got any direct verification that the game takes account of it. If anyone out there has got direct experience, I'd be happy to hear about it.

Basically, my Byz emperor took over, was married, had no perversions but had no heir and then the Royal-blood uncles all started dying of old age, leaving him as the only one left with a crown icon on his parchment. He was advancing into his forties and it looked like my time was soon to be up (his predesessors didn't all die at 56, so that bugfix definitely worked but none of them lasted much more than 2 or 3 years beyond that).

I had married a daughter to my highest acumen govenor and it would be interesting to know how the game keeps track of his potential for a claim to a vacant throne, since the only sign left of such a link is the wedding ring icon on his parchment.

I now have an heir but I'm still not out of the woods yet, since the emperor should be about 62 before the heir comes of age, so it's touch and go which will happen first.

Is it possible to have an under-age faction leader or does the game disintegrate your empire if the successor is as little as one year too young?