Enrique Iglesias has ''more sex than ever'' since becoming a father.

The 'Hero' singer and his long-term partner Anna Kournikova welcomed twins Nicholas and Lucy into the world last December but having twins doesn't mean they no longer have time for one another.

Enrique said: ''It's probably more sex now than ever. The sex has not diminished.''

The couple have been together since 2001, and though they have their ''ups and downs'', the 43-year-old singer couldn't be happier.

He gushed to The Sun newspaper: ''Like any couple, you still go through your ups and downs and it's not always perfect. But it is perfect in a way.

''It's incredible to watch her be such a great mother. It's incredible to watch a mum do what she does, when a mother's instinct kicks in.''

Despite being so happy with the 37-year-old former tennis star, Enrique admitted shortly before their twins were born that he still hadn't introduced Anna to his father, singer Julio Iglesias.

He previously admitted: ''They still haven't met, no. They have to meet at some point.''

The 'Tonight' singer also admitted he and Anna had no plans to tie the knot but they already live the life of a married couple anyway.

He said: ''We're just as happy. There comes a point when you've been with someone for a certain amount of time that I believe that you are like, married.

''I guess the only difference is that we haven't walked down the aisle.''

Enrique raised eyebrows when he introduced Anna as his wife during a concert in Russia in 2011 but he subsequently admitted he simply got caught up in the moment.

He said: ''It was just meant to be sweet, in the moment. I honestly didn't mean to confuse people. I thought it'd be easier for the audience to understand than if I said, 'my girl'.

''I've never really thought marriage would make a difference. Maybe it's because I come from divorced parents, but I don't think you love someone more because of a piece of paper. And nowadays it's not taboo to have kids and not be married.

''What makes a difference is that you're a good parent.''