In a recent study, a group of researchers have found that compared to childless couples, couples with children were as likely to report conflicts with their own parents.
Although relations with in-laws are the subject of many anecdotes and proverbs across cultures, they remain little studied in contemporary societies.
Using survey data from Finland with over 1,200 respondents, the authors studied conflicts that couples reported having with their own parents and their in-laws.
Overall, Finns reported higher conflict occurrence with their own parents than with their in-laws. Compared to childless couples, couples with children were as likely to report conflicts with their own parents.
However, they were more likely to report conflicts with their parents-in-law.
The results took into account how frequently family members were in contact with each other and how emotionally close they felt, as well as other socio-demographic factors.
Previous studies have shown that in-laws become more kin-like to each other when a grandchild unites kin lineages.
Treating an in-law almost as biological kin can make the adults involved feel closer to each other and help each other more, what has been called a kinship premium.
This study documented evidence also of a kinship penalty.
As in-laws become more kin-like through the presence of a grandchild, their mutual conflicts increase.
Childcare provided by grandparents is of great help to parents of young children, but may also be a source of conflicts.
"Daughters-in-law were more likely to report conflicts when their mother-in-law provided more grandchild care," said researcher Mirkka Danielsbacka, adding, "This indicates that the increase in conflicts between in-laws are related to grandchild care."
The study was published in journal Evolutionary Psychological Science.