Probability of Donatello being from a different clutch of eggs.

[victory_angel]

It's doubtful that Nick will go this rout, or if they do they wont go all that deeply. And the only characters who are who are twisted enough to point out this possibility are an Evil Clone of Donatello, or Bishop.

But Bishop not likely to appear much before season 3 and Evil Clones while still probable are also up in the air.

However the being from different a different clutch thing is a concept that hasn't been widely used in the other incarnations. With the exception of Next Mutation, it has been explicitly stated they are all related, or it has been ignored completely.

Mind you that just because one of them could be from a different clutch this would not necessarily mean they are not all brothers. They would still be brothers because they were raised together as a family and have always thought of themselves as brothers. So there would be no reason that would change.

But at the same time however, it might bring in a different perspective on some behaviors the other Turtles have towards Donatello. Such as forgetting he exists.