The 40-year-old singer gave birth to Max and Emme in February 2008, after years of thinking she would never have children. Although Marc already has three children from previous relationships, he was overwhelmed when he heard Jennifer was carrying twins. "Marc started crying," the singer recalled. "It was a joyous time. We were happy... He`s emotional! He just couldn`t believe it was happening. He`d had children before and this was like a whole new, special experience. "I was in denial that I was even pregnant at first, so when I found out I was having twins, I just kind of laughed like, `Of course this would happen!` And then I started giggling." The twins are now two years old and Jennifer and Marc say they`ve never been happier. Jennifer loves motherhood, but admits it is starting to get more difficult to leave her children when she goes out to work. "They`re at the point now where they`ve come to the door and started yelling, `No, no, Mommy, don`t go!` And I was like, `Whoa, this is bad.` That`s really tough. So I`m just going to have to figure it out as I go along. I keep trying to explain to them, `I`ll be home and the sun will still be out!` " Jennifer plays a single mother in her new film The Back-up Plan, and admits she has no idea how women cope raising children alone. She is constantly surprised by how challenging motherhood is and is certain she couldn’t manage on her own. "It`s just too hard! Honestly. I have so much respect for single moms or anyone who finds themselves a single mother - but to choose to be a single parent is courageous. "It`s such a hard job to raise a child and to be everything to that child without a partner... I don`t know if I could do it on my own, I really don`t."