When Mr Lai Shehui arrived at his home in Chaozhou, South China's Guangdong province, early this month, he found his wife and son dead.
Their hands and feet were tied.
His daughter-in-law from Vietnam and his two-month-old twin grandsons were missing, China Daily reported.
About 15 hours after the murders were reported, the police found his grandsons and the Vietnamese woman in another town, where she had intended to sell her babies.
The buyers and broker involved in the baby trafficking case have also been arrested.
According to the police, the 21-year-old known as A You and her three male Vietnamese accomplices allegedly strangled her husband and mother-in-law when they stopped them from making noise at her home.
Mr Lai, 60, said his daughter-in-law was "bought" for 28,000 yuan (S$6,270) from a matchmaker last year to marry his 32-year-old son.
Said Mr Lai: "Because she is expected to carry on the family line, we did not ask her to work a lot."
But since she was pregnant last May, she has run away from home repeatedly before she was subsequently found, he added.
He claimed the matchmaker was a middle-aged Vietnamese woman who has acted as go-between for Vietnamese women and Chinese bachelors for years.
Local police said because the Vietnamese brides have no "hu kou", or household registration, and their marriages are illegal, they have difficulty fitting into the local culture.
As a result, many of them run away from their husbands soon after they are married and go on to sell themselves to other Chinese bachelors.
Illegal cross-border marriage is nothing new in China, especially in some impoverished villages where bachelors find it difficulty to marry a native bride.
It is partly due to the gender imbalance as well as tradition, especially in rural areas, where the men are the only recognised heirs to carry on the family line.
Also, many women in the villages move to cities amid rapid urbanisation.
This article was first published on Mar 21, 2015.
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