updated 04/25/2010 AT 8:00 AM ET
•originally published 04/25/2010 AT 9:00 AM ET
Newcomer Aaron Johnson has a lot of reasons to smile. His superhero film Kick-Ass was the number one movie at the box office last weekend, and off screen he’s engaged to be married to his seven-months-pregnant fiancée, British artist Sam Taylor-Wood.
Life could not be any better – if only his relationship with his onetime director wasn’t raising so many eyebrows.
At 43, Taylor-Wood is 24 years older than Johnson and already a mother of two from an 11-year marriage to art dealer Jay Jopling. Despite the age difference and existing family, Johnson is madly in love. “I’ve got a wonderful woman,” says the 19-year-old. “She’s lovely and she’s a fantastic mother.”
The two met in 2009 on the set of her directorial debut, Nowhere Boy. In it Johnson played a young John Lennon and the two immediately hit it off. Engaged months after meeting and already living together, Johnson brushes off critics about their whirlwind romance saying, “I’m an old soul and she’s a young soul.”
As the couple prepare for the arrival of their baby this summer, Johnson says he’s “excited” and insists that he is undaunted by the challenges of fatherhood. “It’s not scary,” he says. “I’m already a stepdad to [Taylor-Wood’s kids Angelica, 13, and Jessie, 3] anyway. So the nerves have sort of gone.”
For more from Johnson and his relationship with Taylor-Wood, pick up this week’s issue of PEOPLE, on newsstands now