I think about this at least once a day

Okay, now I can't get it out my head that 17 yo Cassian had a massive crush on (18 yo?) Azriel but bc of the Illyrian education he didn't really know he could love a male romantically. When Mor visited and Az fell for her, he was so jealous of the attention his friend was giving her, that when she asked Cassian to bed her, he did it out of jealousy. But then Az discovered and was so pissed at him that Cass knew that he wouldn't have a chance anymore, and Az would never love him like he loved Mor, so he suppressed his crush down to the bottom of his heart and forgot about it.

Years later, when he went to live in Velaris and started trying new thinks, he took males to his bed, but it was never more than that, because unconsciously he just wanted one male in particular to give him that kind of love, the same for the females. Then centuries later, he grew used to, and kinda enjoyed, being a buffer for Moriel because it meant they wouldn't be together, and he unconsciously wanted Az to always consider him in the path to his happiness, because Cassian would not, could not think of anyone else to share a family and the rest of his life with.

Until he met Nesta. That just like Azriel, wasn't someone so easily seduced by his quick grin and unfaltering arrogance. Not because it was new, but because it reminded him of his youth, when he was a young brat and met a certain shadowsinger, no matter what he did, Cassian couldn't read him. It made him feel like walking on eggs all the time, and the lack of control was so amazing, it made him want more. But he didn't get it.

So he just added that to the fact that he already felt like he wasn't enough for anyone to love him solely for who he was, and covered that insecurity with those crooked smiles and swagger, so nobody could pry inside his heart, that for a male so big, tall and muscular, was just the heart of a child who only wanted someone to hold him tight and told he would not be let go away an he would always have someone there for him, just like he was for everybody else.

But unlike Azriel, Cassian knew Nesta had felt something similar for him, and he saw a light on the end of the tunnel, a sparkle of hope, and like everything he ever had in his life, he decided he would fight for it, and he would get that love because deep down, he knew he deserved it.