"Mother," Kelvin beamed brightly at the woman he has come to learn to embrace as his own. While Genevieve was Gabriel's mother and nothing would change that, Kelvin has become so attuned to his role that it has become second nature to smile at her. Moreover, the woman was nice - and surprisingly treated him better than his own mother.
Sure, his own mother loved him, but Genevieve protected Gabriel with a fierce stubbornness and perhaps that might have to do with the fact that she was determined to keep him alive against all odds. Kelvin was not the only child or son of the family, hence the attention was divided.
Even if he died today, while his family would weep and mourn, they would probably get over him in a year. They had to move on and there were their grandchildren to worry about. Hence, he didn't worry about his brothers checking up on him and finding him missing.
