Mark had an interest in Mickey from the moment he saw him. The color of Mickey’s eyes played a part in it too. After meeting Mickey, his interest grew into something that he wanted to further explore. Kind of like love at first sight. Once Mark established a friendship with Mickey, he discovered just how much he really liked the guy. Add to that his suspicion that Mickey might be like him preference-wise. To Mark, a relationship becomes truly meaningful when it becomes sexually intimate; thus his desire for a sexual relationship with Mickey when the tide turned with the kiss. Mickey is complicit, too, by seeking out Mark’s class, inviting Mark to dinner and meeting his mother (his main objective) and initiating the kiss. From there, they both wanted more, which happened at the falls and then later in this chapter. But I agree with you, Mark’s terminology could have been more considerate in this instance. “Made him mine” is not meant to be possessive, but endearing and intimate. Thank you for the comment, Peter.