I Am Distraught

I think that Laurent Aden, the privateer that Anjelica ran away with, is Cas, Kel's friend from the Orfelinat. Here are the reasons why:

Their descriptions match! In Sword Catcher prologue, Cas was described to have blonde hair, blue eyes, and freckles. We learn in Ragpicker King that he has blonde hair & blue eyes.

Laurent states that Castellane is "the place of his birth" during his POV.

The only times Kel thinks of Cas during Ragpicker King is when he's thinking of Laurent Aden and reminisces on how he and Cas wanted to be pirates when they were young.

Kel never sees Laurent up close/face-to-face. He sees him in person at the Solstice Ball but Laurent has a mask on his face, and Kel is far away from him. The single time they interact is when Kel is in Anjelica's room trying to convince her to not leave and Kel hears Laurent speak out the window. They never see each other but...Kel RECOGNIZES HIS VOICE, saying his voice was oddly familiar but he couldn't place it. He thinks that maybe he heard his voice at the Solstice Ball, but they weren't even in the vicinity of one another. This is the biggest piece of evidence that Laurent is Cas.

In the final scene with Laurent waiting outside for Anjelica, Laurent literally says to her that she should tell Kel that he needs to get out of here and that there's enough room on Sedai for Kel to escape with them. He obviously knows who Kel is and wants him to escape with them and live.