John Matthew is introduced in Lover Eternal. His entire character rips into a certain paranormal genre cliche but I'll leave that be since it is a massive spoiler.

The most whiny emo of the brothers is Phury, truthfully. I mean, Vishous did engage in some crazy angsting in book 4 but that was more lovesick mooning than Phury, who not only does lovesick mooning but also does whiny emo bitching in book 5. ("I am more special than you!")