If I recall correctly, such a resemblance was a clue in Conan Doyle’s The Hound of the Baskervilles and in some other mysteries (not noted until later).
It’s not just a plot device, there are families like this and they’re not all wealthy or prominent, or at least not anymore they aren’t. Me, I’m too much of a mutt I guess, despite having a few illustrious ancestors I’ve also got some who were pretty darn common to the point of being from the wrong side of the tracks, and then a whole bunch who did OK in life but left no lasting impression other than their descendants. If I look like anyone facially it’s my maternal 2nd great grandmother and I’m male. I have my father’s build and bone structure. Look sort of Scottish apparently, or even Spanish since I’ve had Mexicans walk up and start speaking it to me thinking I’d speak the language as well. Cousins all over the map, fair, olive, freckled, blonde, brown, red, even almost black. You’d never know most of us were related from appearance alone. My closest male cousins paternally are the only ones anyone might think were related, oddly enough, but they’re browner than me.