Leia's step faltered only for a brief second. Somehow it hadn't occurred to her that there might be more than one, but of course there would be. She'd always been lonely, growing up; she'd had her best friend, Winter, but had longed for a brother or sister of her own. Finding Luke had been finding part of herself that'd always been missing. Of course if she had children, she want to make sure they had the experience of having siblings from the start.
But they couldn't be here, or she'd have heard about them, or Han would have. Poor Jaina. Leia's expression was sympathetic as she said, "They're not here with you?"