More fun thoughts, especially for the AUs where Doey’s one person and can't split, you think he ever gets annoyed with himself and addresses those behaviors as the kids? Finds himself getting annoyed or irritated and goes something like "Kevin, calm down." Or feels like he's getting too giddy or exuberant and it's like "Jack, Jack, wait, this isn't a good time-!". Or feels anxious from the pressures around Safe Haven, and just quietly goes to himself, "Matthew, we, we can't do anything else, okay?".
He's not even sure if this is a case of him seeing connections where there aren't any, and maybe he just looks crazy for doing it, but sometimes it helps? Or, feels helpful? Maybe makes him feel a little less awful over his whole situation. But, much like the Fandom, can see Doey having the most 'talks' with 'Kevin', given that I can definitely see the temper from him mixing horribly with other frayed nerves. Doey snapping or withdrawing from a moment with the others because it stamped on some trigger he barely remembers the context for, but he immediately assumes it's from Kevin. And goes on a bit of a frustrated tirade, trying to stay quiet so as not to worry anyone but still growing more and more upset as he rambles "I don't know what happened to you, but we can't keep doing this! Not everyone trying to hug you is gonna hurt you, they can't even hurt me, they're tiny! ...Why are you always doing this, Kevin?! It's not fair! I don't wanna be angry, I don't want people looking at me like I'm gonna hurt them! I don't want this to be Susan and George all over again, Kevin! So just STOP, okay?!"
For extra poignancy, Doey turns enough that he's facing some sort of a reflective surface, it hammering in at that moment that there is no one else here. No Kevin. Kevin can no longer respond, if he ever could, and Doey’s just basically had this whole yelling match with himself. At a more metaphorical than real child who did not ask for this to happen to them.
Can imagine he has to sit with that realization for a good, long while.