We could go a bunch of different ways with this one. I imagine Serafina might know about them, like as a contact overseas if they were both into some similar stuff with selling...I suppose she could always find out from her little dark hunter lover who did it for Sorcha?

Alternatively, Alexander could have certainly killed them but he would have needed a reason to do it. He's not really the kill people just because they are witches thing. I mean, I don't know what you have planned really but that could always be a twist too if you wanted - if like they did some dark stuff and Sorcha finds out from her parents killer that maybe they weren't all that good afterall? I dunno, I'm just spitting out ideas haha. I don't want to ruin anything you had planned on that front :D