Family Resemblance
Hollywood hardly ever paid close attention to whether actors playing relatives resembled each other. However, I found it easy to look at Charles Bickford and believe that Lee Remick is his daughter.
Ditto Bickford and Carroll Baker in *The Big Country* - Remick and Baker had the same type of beauty.
It might be kind of fun some time to make a list of 'most ludicrous casting of relatives.' One might start with *Where Love Has Gone* with Susan Hayward as Bette Davis' daughter, and Joey Heatherton as Susan Hayward and Mike Connors' daughter. There are many, many examples...