I think he started closer2closure back when he was like 17. He's been around for a bit, SWS is almost 2 years old now. I'm sure his high-pitched vocals make him seem younger than he really is.
I enjoy both of their albums. Kellins voice is golden. But of course that's just my opinion and a lot of people on here will join the fad of hating on any band that isn't accepted by their peers, therefore I doubt many people will agree