I've thought about this too. I think the only sane option is to maintain a quiet life where you occasionally privately name drop to help your own networking. Who'd begrudge a sibling getting ahead in life with a little help from you? But meanwhile there is this. Can't imagine the internal dynamic between them w.r.t. how this portrays his hard earned professional image, I imagine words have been spoken

Maybe I'm a bad networker because it would never occur to me to namedrop a famous relative. Nor do I know it would be that useful, unless you want to act as a second appointment secretary to your relative filtering out deals to bring them.

I imagine you could couchsurf to the various vacation properties off-season when they would otherwise be empty, which would be nice.