twins:robert and cameron Good twin = cameron bad twin = robert. Atm cameron is in a coma in a hospice somewhere so robert is pretending to be cameron at the robinson place
It's to pay back everyone for being so mean to him all his life as Cameron was the favourite (now in coma) and he (Robert) was the one that was ignored or made fun of.
It's no secret that he caused the plane crash. He 's now picking people off one by one. He's also nuts which doesn't help. Do you follow ......?