Their story has become a national talking point in Syria after the girl's father relayed the story of their engagement to the Akes Alser website.
The families of both children have won plaudits over the union — although they insist the children are in love and want to marry.
Khalid's father, Juma, said the boy was his only child from a 25-year marriage.
"I vowed to have my child engaged at the age of five if he was a boy and to marry him to a woman of his choice at the age of 15," he told Gulf News.
Juma said Khalid, from the town of Horns, 180km north of Damascus, fell in love with Hala within days of meeting her during a family trip to the port city of Latakia.
He claimed Khalid was so love-sick after parting from his young girlfriend that he refused to go back to his nursery unless little Hala came too.
"We did not know what to do till my wife called Hala's mother and asked her opinion about the case," Juma was quoted saying.
"She said her daughter had developed similar symptoms of loneliness and the family would be happy to see them engaged."
Juma bought rings for the young ones and both families held a celebration in Latakia.
The father has even vowed to cover the education expenses of both children until they graduate from school.
"We know that Khalid or Hala might change their mind in the future, but what we do know at this stage is that they are very happy and talk to each other everyday," Juma told Gulf News.
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