“Here, son! Play with these dolls ACTION FIGURES of scantily-clad muscle men in loincloths! That oughtta keep you hetero!” 
“Here, son! Play with these dolls ACTION FIGURES of scantily-clad muscle men in loincloths! That oughtta keep you hetero!”
Apparently they’re roughly 15…
Boyhugging with a backpat and a “proud 'a you, son”
Yeah, in the 1980s series, they’re canonically all 15. It was printed on the toy packaging and in the mini-comics that they had back in the day.
You can probably pull the “wull ackshually a 15 year old turtle is like a 1,000 year old dragon” card here, and then we can
you for entertainment purposes.