I know it's not the same, but there is a 15year age gap between my child and my sibling. My sibling adored my child, when both were young. Now they are old (sibling coming up 70, child in their mid 50's) my sibling still thinks the sun shines out of my child.
When our Mum died, child's beloved Nan, I repeated to my sibling that my child had been quite nasty to their (childs) partner. Child had told me this themselves, and I was aware of how cut up about the death child was and saw that as a reaction to their hurt, not excusable, but understandable. My siblings response? "Oh no not xxx, they couldn't be nasty if they tried".
True, they didn't always have to live together, but they did for some years. and sibling always went out of their way to keep in touch with my child when we didn't all live together.