Identical twins may share more than their genes. In some families, adult twins see themselves as auxiliary parents to their nieces and nephews.
Because identical twins are genetic copies of each other, their children share half of their genes with both their parent and the parent's twin. Genetically speaking, identical twins are parents to each other's children.
To investigate whether these close genetic ties affect family relationships, Nancy Segal, director of the Twin Studies Center at California State University at Fullerton, and Jim Seghers, a graduate student, examined bonds between some 300 sets of identical and fraternal twins and their children.
Segal found that aunts and uncles who are identical twins say they feel closer to and more involved with their co-twin's daughters and sons than do fraternal twins. More than 60 percent of the identical twins in the study thought of their co-twin's kids as their own.
One pair of identical twins in the study, Jill Sigel-Greer and Judy Sigel-Freeman, said they feel like mothers to each other's children, sharing the same feelings of pride and concern for their nieces and nephews as they do for their own kids. Jill and Judy's children even call their aunts "Aunt Mom."