Alek doesn't want to give her false hope, but he also can't help pointing out a real possibility.

"He could always fall through the rift, too," he says to her. It wouldn't be the first time it's happened. People don't always fall through the rift at the same time, but there are reunions. Which can be confusing, depending on the different points in time they arrive from, but she would still have her brother. Alek wants that for her.