Cassian absolutely adores Jayce's mother. She was the most of a mom he'd ever had, and he saw himself forever in her debt. Ximena was kind to him, so kind. She went out of her way one day, the night after Briar's funeral, to tell his dad off at her front door, when he demanded Cassian return home. He admired her efforts, even as a lower house. She's showed him more care and compassion than any higher house he's ever seen, and he could never forget it.
Even after he returned from Cadet school, he clocked into the labs one day and was surprised to see her in the room, talking to Jayce. It had been the first time Cassian had seen her in 4 years, and even so, her gentleness never went away.