I think with probably having time from leaving school to get a lot of proper groundschool instruction in, an amazing amount of flying experience- all at great expense (probably in the region of 50-60,000 pounds) if you have that amount of money available in the first place, then age is no barrier. Most people feel extremely fortunate if they can struggle to get their ATPL by the time they are 30- the dedication is quite extreme doing all that work and expense on top of trying to live a 'normal' life with that bug inside you. Bit like asking 'is there a minimum age for a degree?'- well no, if you're clever enough to get one. But if you are resourceful enough to worry about a minimum age for an ATPL, you will be resourceful enough to find where the answer is to be found?