Shmi Skywalker is the mother of Anakin, she was a slave in Episode 1, but a minor NPC otherwise. The father of Anakin is said to be "The Force". Anakin Skywalker was a Jedi Knight class who was bought out of slavery by Qui-Gon Jin (Jedi Knight) and subsequently married Padme Amidala, diplomat and gunslinger. Of course due to his mother's death and the influence of Palpatine (Sith Inquisitor), Anakin gained many dark side points and at the end of Episode 3, actually changed class to the Sith Warrior class.
Now the step brother of Anakin was Owen, who later married Beru. They are mere moisture farmers and thus again NPC class in SWTOR.
Anakin and Padme had two children; Luke and Leia Skywalker. Luke was later to become a Jedi Knight class again, whereas Leia was again a diplomat/gunslinger like her mother. Luke was raised by Owen and Beru Skywalker, whereas Leia was raised by her adopted parents Bail and Breha Organa.
In the expanded universe there are offspring from marriages between Leia and Han Solo (Smuggler), and Luke and Mara Jade.
So there is plenty of opportunity to tie up Republic and Sith, and different classes into a Legacy.