Ostiller's children are old enough to wonder what people mean, she explains. Identical twins occur when a single egg splits in two, creating two babies of the same sex. Interestingly, the rate of identical twin births in the U.S. is the same as it's always been, while fraternal twin births are growing dramatically. Only fraternal twins run in families. Identical twins happen by chance and can happen to anyone, whether there are twins in the family or not.
Different races have different probabilities for having twins, too.
Joe, whose identical twins were a complete surprise, says she is really in the minority because she had her twins when she was under 35, and she is Chinese. Some people think having twins or triplets is the same as having two or three children in a row. Potty training multiples calls for unusual measures. Ostiller trained her triplets all at once. I waited till summer and got three potty chairs for outside.