Foster met Ljungberg while he played for West Ham in 2008. The two kept their relationship underwraps desite a Seattle Sounder fan posting Natalie's name in a forum. It wasn't until his move to Celtic that the press got wind of the pair. Due to his dwindling career and lack of publicity, the couple were able to have a low profile. In January 2012, Ljungberg's publicist announced that Foster and Ljungberg were expecting their first child in March.
The publicist defined their relationship as partners.