Board Thread:Questions and Answers/@comment-33790467-20190220205255/@comment-995426-20190222133831

Yes, but the specific mental ages of each of them are murky. We know that in their human lives, the blue son was older than the red son, who was older than the purple son, who was older than the orange son, but all were teenagers when they died. Assuming none of them are twins and there were no premature births (none of which I can't say for certain, but for the sake of this thought experiment), that would mean that each of their births were separated from one another by at least 9 months, making human Leo at minimum 27 months (2 years and 3 months) older than human Mikey. So if there have already been three Christmases since they mutated plus at least several months when Raph was still living on his own, then right now Mikey's minimum age is 16 or 17, which could likely make Leo already 18, 19, 20 or older. Their childhoods are probably already coming to an end, which is just as well because that's what's eventually supposed to happen.