Simon Cowell and Lauren Silverman are like ''two teenagers dating''.

The music mogul - who is expecting his first child with the New York socialite following a passionate affair - has been inseparable with the brunette beauty since she touched down in the UK, and Louis Walsh believes she's the reason the no-nonsense 'X Factor' boss has got the spring back into his step.

Speaking to the Daily Mirror newspaper, he said: ''I went out for dinner with them. I think he's going to be a great dad. She's a great influence on his life - very positive and bubbly. She seems to have got the fun back into his life.

''They are like two teenagers dating. I love Lauren. I love all his girlfriends. He is what he is.''

The 53-year-old star previously said he hadn't ruled out tying the knot with his pregnant lover after learning that he was soon to become a dad for the first time, but he said people would need to ''wait and see'' if he pops the question.

However, Louis is convinced Simon will whisk Lauren - who is believed to be three months pregnant - down the aisle before their baby is born because he's ''old-fashioned'' and likes to follow tradition.