Under different circumstances, maybe in a different lifetime, Renlin might have been able to fill some of the void that Isaac had left in Tae’s life. In this life, however, Tae couldn’t remember a time in his life when his cousin didn’t resent him. As a child, he naively thought that he might be able to fix it, to make him like him. After the accident, he didn’t have the energy or willingness to continue to try and so he gave up, finally recognizing that any hope of their relationship getting better had died in the car with his brother.