Brother didn't know what he'd been expecting when he asked. Months ago, it might not have surprised him to think of Morrigan doing something so short-sighted and selfish. Now, it did, possibly because he thought that, even as mean a bitch as she could be, she made an exception for him. Which proved to be wrong.
There was a little spiteful part of him that was glad that she was hurting when he asked her these questions, but mostly he just felt empty. "That's it, then?" he asked, not quite managing to laugh. "You just... didn't care about me because you needed to be distracted? It could have been avoided if I had just been home at the time?" In the wide world of irony, being cheated on because he'd been out trying to save his girlfriend's life was probably near the top.