Donovan is from the first batch of clones. To explain his character, I need to explain the clone Michelangelo (They refer to him as Mikeal so he isn't confused with THE Michelangelo) Mikeal was the 'weakest' of the first batch of turtles, and Shredder needed something to make sure that Leon, and the other two, wouldn't rebel against them, so he let them grow up together, before isolating Mikeal, as well as punishing him for things the others had done, and completely, absolutely mistreating him. As a result of all of this, Mikeal gets sheer red eyes from one of the experimental poisons, which cause him to lose sight of color and as time goes on, makes him blind, as well as smaller, thinner, and sicklier than his DNA donor. Donovan was the closest to him before they were separated, and it just tore him up whenever Mikeal was mistreated, more than the others. They were only allowed to see him once or twice a week, and sometimes they weren't allowed to if they disobeyed or failed on a mission. Mikeal later dies because of all the chemicals and poisons that were injected into him. Mikeal didn't tell his brothers, knowing they would force him to get treatment, or if it was too late, Shredder would imprison a different brother. but he knew that if he waited for final good-byes, his brothers wouldn't be tied down to the Shredder's grasp, and they could be free. (The only reason I didn't do Mikeal as a picture was because firstly he's dead, and secondly, no picture could do justice to what was done to him) Donovan is hit the hardest by his death, but he slowly recovers, later pairing off with andrea, who's light-hearted spirit reminds her of Mikey. But because of this, he is even more with-drawn, sad, and isolation-inclined than Donny.