(Cover) - EN Showbiz - Joel Madden says the secret to a happy relationship is keeping your d**k in your trousers.

The 31-year-old is married to socialite Nicole Richie, 29, whom he starting dating in November 2006. The couple confirmed their engagement in February 2010 and married in December. They have two children together; daughter Harlow Winter Kate, three, and 17-month-old son Sparrow James Midnight.

Joel, who is the lead singer in rock group Good Charlotte, reveals he has learnt the secret to a happy relationship since meeting his wife.

I guarantee that if you stick to this rule you will have a successful relationship. Its that simple, the singer told Kerrang! magazine. No matter how much you f**k up, no matter how thoughtless you may be, no matter how bad a listener you may be as a man, if you dont f**k anyone else your relationship will stick and you will be trusted.

Joel started dating Hilary Duff in 2004, when she was 17 and he was 25. In 2006, after two and a half years together, the pair broke up.

Despite finding the key to a successful marriage since meeting Nicole, the singer has admitted he was hardly ever faithful previously.

How long did it take me to learn that? Pretty much every relationship Ive ever had until the one Im in now, he said. (C) Cover Media