Aahh there certainly are quite a few which make me wanna check the comics! Cool designs, really.
Hmm.. since his sister didn't make an appearance in Heirs of the Crown yet, I'll take Endres because I love him just as much. I don't have a single picture of him alone in his usual stuff, so I only can serve with this pic of him in modern day clothing (his hair is usually braided in French style at the sides, the rest tied back if needed):
I love him quite a lot, he's calm, mindful, and actually just wants people to let him be and not be used as a chess piece against his sister (since she inherited the throne). He studies to become a healer (which will come in handy later as well), plus I can identify with him probably the most out of the three protagonists.