> There is no guarantee your children will take care of you

On the flip side, for those childless, it's completely guaranteed none will.

> One quarter of adult children estranged from a parent

That sounds like a 75% success rate.

doubtful 75% is all high quality. The one quarter is probably all really bad, then some of that 75% is bad enough that it won't make much difference. Probably 25% is so into their parents that they will actually take care of them.