Luke isn't used to advertising their relationship yet. He prefers to check with Leia before he tells people, but this situation is so far from 'usual' as to be meaningless. "She's my twin sister. We met when we were nineteen and she sent a message to an Obi-Wan Kenobi asking for his help. I ended up with the droids carrying the message. We went to save her, she ended up saving us, it was a thing."

He looks away, to his hands in his lap. "We found out last year. That we're twins. Ben never had a chance to tell us and Yoda... chose not to, which I can't entirely blame him for." If he'd carried that knowledge to Bespin, he would've doomed them both. "So she's Leia Organa and I'm Luke Skywalker and I don't think either us quite knows how to handle telling people."