Ailyn Vel is the daughter of Sintas Vel and Boba Fett. She always hated her father for abandoning herself and her mother. Her hatred only increased when, one day, her mother never returned from a mission. Ailyn worked as a bounty hunter as an adult. In order to ruin her father's name, she wore a set of armor that looked very much like Boba Fett's and used his name for some time.
In 40 ABY (After the Battle of Yavin), at 55, Ailyn Vel - utilizing the identity Ailyn Habuur - took a bounty on the Solo Family by Thrackan Sal-Solo. She was, however, captured while in hiding on Coruscant, hunting her prey. She was taken in by the Galactic Alliance Guard, an elite anti-terrorist unit controlled by Colonel Jacen Solo. Ailyn was interrogated by Solo for some time. He utilized the Force to rip the information he desired out of her, killing Ailyn Vel.
Boba Fett, who wanted to reconcile with his daughter, hated Jacen Solo for what he did. He took in Mirta Gev, Ailyn's daughter, and he started learning about his daughter through his granddaughter, and the two started to gain something of a fond relationship - one he never had with his daughter.