Parents are keen to find playmates for their children and many opt for boy-girl arrangements to prevent fighting over toys. These "doll marriages" can be cute and harmless, but a psychology expert says parents better not emphasize one gender over the other.

A baby boy and baby girl play together with the help of their parents in Shanghai.

Child betrothal was once common in China, especially in the countryside. A girl and a boy were betrothed when they were born or were still children since their parents believed the two families were a good match of equal standing.

It was known as wawa qin or "doll marriage arrangement."

These scenarios, which prevailed in many parts of the world and still take place in some societies today, sometimes led to tragic mismatches, star-crossed lovers and situations dramatized in books and films.

Of course, in many cases children grew up naturally to accept that their wedlock and future were mapped out by their parents and could not be challenged. And some people do marry their childhood sweethearts.

Today, a playful take on "doll marriage" is becoming popular among young Chinese parents who set a son and daughter up to be tiny playmates, then bigger playmates and best friends.

"This is more like a fun game to create a relaxed and light-hearted atmosphere between friends," says Brian Sun, a 36-year-old IT specialist and father of a four-year-old boy. "My wife's best friend has a 3-year-old daughter. Our families always hang out together during weekends, so we kid each other that my son is her daughter's 'little boyfriend.'

"Guess what? I gave the little girl a box of chocolates on Valentine's Day and said it was from my son," he says, laughing.

This "engagement" or "dating" is more like a game for parents.

Jasmine Jiang, a senior marketing manager at an international company, says: "My son has three 'wives' already. I don't see anything wrong with this. It actually seems to shorten the distance between my friends and me as well as my kid with their kids."

The play dates and venues for these little boys and girls are similar to adult dates. They go to movies, art museums, amusement parks, restaurants, and so on. Some children even go on overseas trips together with their parents, when they are in each other's company most of the time.

"I am just back from a trip to Hong Kong Disneyland," says Rebecca Wu, a mother of a 10-year-old daughter. "I feel fortunate that I found her a playmate to come along. The boy and girl had a marvelous vacation. They chatted about everything from school and computer games to music while also secretly exchanging views on their parents."

In fact, her daughter and her friend's son actually met when they were still newborns. The boy's mother is Wu's high school classmate. Before the birth of their kids, the two parents had already agreed to let them be playmates in the future. In Wu's eyes, Chinese children are too lonely because of the one-child policy.

While these play dates bring kids together, it also can widen the social circle of their parents.

"My boy has a g0ood girlfriend at kindergarten, so I invited her to my son's birthday party," says Wu Qing, a stay-at-home mother. "Now the girl's mother is one of my best friends who is also a stay-at-home mom."

But if it's playmates parents seek, why not find a boy for a son and a girl for a daughter?

"This is the sex difference," says Christine Wu who has a 4-year-old son. "I tried to find playmates for my son earlier and he does have some male friends. But boys can't stay together long, they are too noisy and fight often. Once I invited a boy from his kindergarten, and they nearly broke apart our house and the neighbors complained.

"It's similar with two girls. Usually when two girls play together, they would compare their appearance, their clothes and their toys; girls are more sensitive than boys," Wu explains.

Her views are shared by Jin Qian, a young mother who just failed to patch up an all-girl play date for her daughter. "When two girls are fighting for the same toy in front of you, it's hard to find a way to balance it out," Jin says. "Every time, the play date ends hastily with one girl crying."

This is also the reason why Wu found a "little girlfriend" for her son. "They seem to complement each other. The boy is braver and he learned how to protect a girl. The daughter's mother is also happy, as my boy also can help her daughter overcome her timidity. They get along very well with each other."

Feng Yalan, a local psychology consultant suggests parents not "give judgment to the kids regarding the gender of their playmates."

"In the eyes of a kid, there is not much difference whether their playmate is a girl or a boy. The parents better not emphasize that the kid must play with a girl or a boy. It can affect the way they think of the sexes later in life. It's better to just let them choose their playmates," she says.

Will frequent communication and contact between young boys and girls affect the future relationship between the two?

"There is an old Chinese expression called qing mei zhu ma (literally "green plums and bamboo horse," a popular childhood game), meaning a man and a woman who had an innocent affection for each other in childhood," says Xu Wenwen, a university student in Shanghai. "I had such a little girlfriend, but we lost contact when her family moved to the US. For me, she is still a friend, and that's all."

But Xu's mother regrets the separation. "I like the girl very much, and we are very close to her family," she says. "In my eyes, she is a perfect match for my son as both the families know each other very well.

"Yet life can't be planned. Even if she was still here in Shanghai, the possibility of a real engagement would have been slight," says the mother.

"Everything changes rapidly nowadays, no one can guarantee any fixed relationship. But I believe the sweet childhood memory between them is precious to both of them."