NEW PHOTOS! Jennifer Lopez's Twins!

My, how they've grown!

Jennifer Lopez's 1-year-old twins visited their mom on the NYC set of her new romantic comedy The Back-Up Plan, Thursday. Lopez's mother Guadalupe was spotted looking after the babies while the actress filmed her scenes.

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With her curls tied up with a bow. Emme wore a floral sundress while her brother Max sported a white shirt and checkered shorts.

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As Lopez gears up to turn 40 next Saturday, she isn't ruling out giving Max and Emme a sib. That's why she still is holding on to her pregnancy sweatpants.

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"Who knows if I get pregnant again?" Lopez told Rachael Ray earlier this year. "I might need them!"