>>34289288>>34288577Going with Lucas and Dawn's heights and weights they are as old or younger than Johto's protagonist so 11-12. Hoenn's protagonist is confirmed to be 12 at the end of the story so I'm pretty sure at the end all the japanese boys are 11 when they start their journey and 12 at the end (which would still make Red the oldest and first protagonist like GF loves).
BW were confirmed 14 in Famitsu (although they were planned to 16 years old teenagers at the start and that's even their age at the Special manga). I guess that makes BW2's protagonist 14 years old too.
XY's are the less obvious ones since they are older than Emma (which is 16) but we don't know how much older and Emma even calls you an adult (18 is legally adult at France tho, so I guess starting at 17 and ending at 18 seems right)
I wonder how old the next protagonist will be, I loved XY's being that old instead the classic little kid