Who is Luke Skywalker's sister?

I'm curious to know, could you please clarify who Luke Skywalker's sister is? It's a detail that has piqued my interest, especially in the context of the Star Wars universe. I understand that Luke is a pivotal character, and I'm eager to learn more about his family ties, particularly his relationship with his sister. So, could you kindly shed some light on this matter? I'm looking forward to your response.