This contains spoilers regarding the Star Wars movies. Do not read in the most unlikely case you haven't seen and want to see them.
I'm referring to the movies here only, because I know only a little about the Expanded Universe.
Luke Skywalker always seems to care heavily about his father, and even after getting to know that Vader is his father, he never seems to ask who his mother was. After all, the stories that his Uncle and Aunt told him, were not really correct, so anything they might (and have) told him should have been questionable to him, too.
Yet, in the movies he never asks about his mother. His father seems to be his only concern. Does he never care who his mother was? After all, it's at least likely that his mom was a Jedi, too. Is there any explanation in the extended universe or maybe even a scene where he does ask?