McLean had a turbulent relationship with Martin due to his drink and drug addiction and despite finding sobriety in 2001, the couple called off their engagement the following year.
The I WANT IT THAT WAY hitmaker, 26, explains, "It didn't work out with my ex-girlfriend, but recently I met the love of my life, KATIE. She's a performer too.
"I feel like I'm in first real relationship - I'm clear-headed, I'm not partying and I'm not cheating.
"(When I was drinking and taking drugs) I was out of control. Even when my then-girlfriend came on tour with us, I'd sneak off to hotel rooms with other girls."