A New Take on Parent-Child Affinities

As a researcher with a special focus on twins, it is exciting to pinpoint behavior that is first observed among twin families. In the course of writing my 2023 book, Gay Fathers, Twin Sons, I came across two novel parenting features that deserve attention. The couple in question, Andrew (an American) and Elad (an Israeli), met as students in Israel in 2008 and fell in love. They married in 2010 in Canada where same-sex marriage was legal, and started a family in 2016 with the help of an egg donor and surrogate. They had beautiful twin boys, Aiden and Ethan. Andrew's sperm fertilized one egg (Aiden) and Elad's sperm fertilized another egg (Ethan). Thus, the twins shared their mother's genes, but not their father's genes. This made them related as half-siblings, sharing 25% of their genes, on average.

Trouble began when they tried to move to Los Angeles--the U.S. consular officer in Toronto questioned them about the parentage and relatedness of the children. Ultimately, Aiden received U.S. citizenship and Ethan received a tourist visa! This was so troubling to the couple. Eventually the case settled in favor of the family, litigated by Immigration Equality in NYC and attorneys from the Sullivan Cromwell law firm.

I was eager to write up this case in book form; it contained so many timely elements: family, twinship, egg donation, surrogacy, gay marriage. The couple agreed and in the course of my interviews, I came upon two new parenting concepts. Both parents talk about how much the child that was biologically related to them resembled them in many physical and behavioral ways: They called the children "Mini-Me's." But Elad also brought up the topic of affinity for the other child who expressed the traits in his partner that he valued. He had learned of this concept in an Israeli magazine, but could not recall the source. I was fascinated.

Based on these insights, I propose two terms. The first is assortative parenting. Assortative parenting refers to a generally familiar but poorly defined concept regarding parental affinity or attraction for a given child—but not necessarily favoritism. It refers to the close feeling experienced by a parent toward a child who displays behavioral qualities that the parent sees in himself/herself.

The second idea, assortative cross-parenting, defines a previously unrecognized parent-child relationship aspect, namely parental attraction to a child who displays favored qualities shown by the parent’s partner. Both concepts/terms came from my interviews with the same-sex male couple, each of whom had contributed sperm that led to the conception of one twin.

Both terms also apply to families in which parents are heterosexual. Consider this comment from Rhett Butler, a fictional character in Margaret Mitchell’s classic novel Gone With the Wind: “I liked to think that Bonnie was you [Scarlet], a little girl again... She was so like you, so willful, so brave and gay and full of high spirits, and I could pet her, and spoil her—just as I wanted to pet you.”

It is interesting that assortative cross-parenting seems to have first appeared in a novel rather than in the psychological literature. Of course, observant authors who are highly attuned to human behavior are well-suited to perceiving and expressing such phenomena in their writing. Of course, even families who may not experience assortative parenting or assortative cross-parenting may still understand it and endorse it.

Some people may wonder if assortative cross-parenting is easier to see when one parent is not related to a child, as in Andrew and Elad's case. That is really a question that deserves additional research. I would say this depends on how the genes are passed on and expressed. We all know conventional couples in which one parent claims that the child is a near replica of his or her partner.

Regardless of the source of these parent-child relationship features, I believe it is important to develop these concepts and to give them a name. These terms, and the phenomena behind them, should stimulate new research that can bring clarity to overlooked features of family dynamics. Only by doing so can we alert colleagues who may wish to include them in ongoing research programs, as well as the general public, which can better understand the psychological dynamics of their own families.

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It is likely that we will see more families created by same-sex male couples with twins who are related as half-siblings. While no one knows the frequency with which these couples are turning to assisted reproductive procedures for starting families, we do see trends suggesting that this process is on the rise.

Assortative parenting and assortative cross-parenting are not mutually exclusive. It is possible that a parent may experience the first with one child, the second with a different child, or both with two children. Envy or jealousy by one child toward his or her siblings could result if that child perceived unusual closeness between his or her sibling and a parent; however, such understanding would probably not apply to all behavioral domains. It is also possible that a parent might experience assortative parenting and/or cross-parenting with an adopted child. Regardless, recognizing and supporting children’s individual differences are essential components of good parenting.

This essay has been adapted from a longer invited paper in a special issue of the journal Early Human Development.