Do low I.Q.s run in the Skywalker family?
Let's look at the evidence.
Shmi: No idea if she has any smarts, as she has about three lines in the whole thing.
Anakin: A real dumbass. Never understood the Jedi philosophy or the politics of his time, let Palpatine play him for a sucker and took twenty years to catch on.
Luke: Dopey as a kid, did not blossom into a genius later in life.
Ben: Dumber than his grandfather. Let's Snoke treat him like a pet rottweiler, understands nothing but whining and violence. Set to fuck up the First Order empire.
Leia: Galactic senator and rebel general by what, age 21? Understands everything about everybody, force in galactic politics through her life, respected by everyone, even her enemies.
So... does that mean that the evident low intelligence only runs in the male line?