Question: how are owen and beru related to luke?
Answer: Whilst Anakin was training as a Jedi Padawan, Cliegg found Shmi, bought her from Watto, and then freed, fell in love with, and married her. As such, Cliegg is Anakin's Stepfather, and Luke's Step-grandfather. Following on from that, Owen is Anakin's Stepbrother, and therefore Luke's Step-Uncle.