Gambit are pretty much the same age as The Guard now and were the youngest tier 1 team last year.
Chronicle and nAts are still 19 + Sheydos and d3ffo just turned 20 + Redgar is 23.
Trent is 17 + Valyn is 19 + JonahP is 22 + Sayaplayer is 23 and I'm unsure about neT.