Angelina Jolie troubled over the imminent arrival of the twins

A source tells Star that Brad Pitt's partner, who already has four children has loaded up on books and consulted experts about raising multiples, but "she's worried they will live in their own little world, mirror each other's habits and not integrate into the family," says the source. "She says she'll never dress them the same and that she and Brad have discussed putting them in different cribs — even in different rooms!"

Breast-feeding is another major concern for the actress. Since she had such a tough time breast-feeding Shiloh, she's "very worried about nursing two babies at once," the source adds.

She starts "hyperventilating," says an insider. "When she freaks, her voice gets real shrill. Just the other day, she was on the phone with one of her managers, who had to calm her down and tell her that the new babies will be a wonderful blessing and that the other kids will help out."

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