After over a year, I add another mean clone to the group, and the reason he wasn’t seen before is because he ostracized himself from the other three.
 
Unlike his real self, Mean Tom is vain and selfish. True, his real self has short streaks of self-admiration, but never to any huge detriment or in damaging ways, he is sill wholly selfless and is out to put others up. Mean Tom, however, will absolutely not help anyone else in any way, they will never get photographs of them as they are unworthy to his eyes. He sees everypony but himself as ugly, they are offensive to his eyes and sensibilities, subponies. This reason is why he abandoned his clonemates as soon as he saw them, he is aware of them, and he hates him, simple because they are not him.  
He loves himself, to absurd levels. He spends all day just taking pictures of and complimenting himself. He’d kiss himself, he’d marry himself, he’d fuck himself. But his time is as short lived as the other clones, when he badmouths his ‘brother’ after seeing him pass by, he instigates a fight and meets his demise at his brother’s hooves.