In Back to the future part two Marty travels to the year 2015 and takes the place of his son after he's thrown over a counter by Griff.
Marty looks so much like his kid that he's mistaken for him by everyone there.
Now I know they're identical because Michael J. Fox plays both characters, but is there an in universe reason for this similarity?
I'm looking for either something from the films or the people that produced them. If there's nothing like this then I'll also accept answers based on real life biology.