Please don't jump to conclusions about Shawn. JUst because Shawn didn't leave Devlin does not mean he didn't want to. HIs time with Devlin was worse than anything we can comprehend so we can't project our feelings of the situation he went through Devlin onto Shawn.
It seems that Devlin's defense is going to claim that he is asexual and that his diabetes was so severe that he had toes amputated and was possibly impotent. They are going to claim that he was just lonely and wanted the boys to keep him company and play video games with him.