Generally in movies and tv families are just kind of random – kids don’t resemble their parents or eack other in looks or behavior, except for those rare instances where the actors are related
— ziel (@yourlyingeyes) September 7, 2019
Then there is the flip side to how characters who are supposed to be siblings never much look alike: actors who, while unrelated, could easily play siblings, but don’t: e.g., all the movies in which Seth Rogen and Jonah Hill, two unrelated actors who have much in common, play unrelated friends instead of the big brother and little brother roles they were born to play.
I can recall walking into the living room while my wife was watching the first of the Judd Apatow Gang movies, The 40-Year-Old Virgin, and seeing Rogen and Hill on-screen together for the first time, and saying, “Wow, that’s great casting, they’re playing brothers, right?”
I expect to soon see a movie in which Jonah Hill and his look-alike little sis Beanie Feldstein play strangers.
In general, there isn’t much demand for actors to play brother and sister in movies except for low-budget prestige dramas on the theme of “Mom/Dad is going senile, what should we do?”
My favorite of this genre is Robot & Frank.
This is a 2012 sci-fi drama in which Broadway star Frank Langella plays a retired cat burglar who is beginning to suffer dementia.
So his children, played by the extremely good-looking James Marsden and Liv Tyler, buy him a robot to be his minder.
I want a robot to be my life caddy, to follow me around and to hold things I hand to him.
Hollywood is nepotistic so it’s striking how seldom the many sibling pairs of movie stars have been cast as siblings: e.g., James and Dave Franco in “The Disaster Artist” being cast as friends is the norm, while Jeff and Beau Bridges in “The Fabulous Baker Boys” as brothers is the exception.
For example, Casey Affleck has appeared in a half-dozen movies with with his brother Ben Affleck’s buddy Matt Damon, but I don’t recall the Affleck brothers ever playing brothers on-screen. They seem to get along: Casey starred in the first movie Ben directed, the pretty good thriller Gone Baby Gone, but they don’t get cast as brothers.