We just recently adopted two kittens thatare about 2-3 months old now. We had 3 cats before we got them and one of my cats, "Taffy" has taken to the 2 kittens very well. She follows them around and baths them all the time, she acts like their mother. Recently Taffy has been getting swollen lumps around her nipples and they have become red... earlier today we caught her trying to nurse one of the kittens as if it was her own. Could she think that they are her babies, so much that she is producing milk? or could it just be from the kittens tring to nurse? And is this anything I should be overly concerned about? Thanks

It is very possible that she is having a phantom (or fake) pregnancy triggered by these kittens.

Has she been spayed?
Has she had any opportunity at all to be with a male cat?
If so then she may actually be pregnant.

This can happen to human adoptive mothers too, when hormones are released that enable them to nurse a baby they have adopted.