Matt Cassels at Cambridge University says far too little attention has been paid to the significant role of pets in young people's emotions after conducting a 10-year study of 100 families in the UK.
Family break-ups mean that in the United States children are more likely to live with a pet than their natural father, says the research.
According to US data, about two thirds of children live with their father, while about four in five of families with school-age children have a pet.
"The data on pet relationships stood out, as it had never occurred to me to consider looking at pet relationships, although I had studied children's other relationships," said Cassels.
"These children not only turn to their pets for support when faced with adversity, they do so even more than they turn to their siblings. This is even though they know their pets don't actually understand what they are saying."
Such relationships, particularly when it was girls with pet dogs, encouraged more social behaviour, such as "helping, sharing, and co-operating".
There was a therapeutic side to this relationship, he suggested, with the pets playing the role of the listener and being more "empathetic" for children than writing problems into a diary.
The study, he said, showed that it was "valid to talk about child pet relationships in the same way we talk about sibling relationships".