However, the new study, published in the journal PLOS One, adjusted for this, indicating there is a more fundamental reason why children follow their mothers' example, the Daily Telegraph reports.
The findings by the University of Ohio come from analysis of more than 7,000 people over 24 years.
"It's not just divorce now - many children are seeing their parents divorce, start new cohabiting relationships, and having those end as well," said Professor Claire Kamp Dush, who led the research.
"All of these relationships can influence children's outcomes, as we see in this study."
Both the number of marriages and the number of cohabiting partners by mothers had similar effects on how many partners their children had, the study found.
However, results showed that siblings exposed to their mothers' cohabitation for longer periods had more partners than their siblings exposed to less cohabitation.
"You may see cohabitation as an attractive, lower-commitment type of relationship if you've seen your mother in such a relationship for a longer time," Kamp Dush said.
"That may lead to more partners since cohabiting relationships are more likely to break-up."