Seeing that Joan Fontaine died (at 96) made me think of the lifetime estrangement between her & her sister Olivia de Havilland (who is still alive, at age 97). Are famous sisters more likely to be estranged than famous brothers or siblings of different sexes? Dear Abby & Ann Landers. A.S. Byatt & Margaret Drabble. Is it because these three pairs were all in the same profession?
Eric & Julia Roberts come up as a brother-sister pair, and Ray & Dave Davies.
Sibling rivalry is as old as the hills: Cain & Abel, the world's first siblings! Shakespeare, of course, nailed it: King Lear's daughters, Taming of the Shrew, all those kings in all those plays.
But there doesn't have to be an empire (or an Oscar) at stake: any woman who's not an only child can probably tell you that the sister bond is maybe the strongest & at times most maddening relationship you can have.