The two men allegedly behind Wednesday's kidnapping for ransom are lovers who have been living together for more than 10 years.

This was revealed by a woman who identified herself as the mother of 41-year-old Lee Sze Yong, the younger of the two suspects who were charged in court on Friday with the abduction of Madam Ng Lye Poh, 79.

Lee's mother, who wanted to be known only as Madam Seow, said her son and 50-year-old Heng Chen Boon - the other suspect - share the Hougang flat with her. She told reporters, who were outside her flat on Friday, that Lee was her only son. "My son is in trouble, of course I'm very sad," she said in Mandarin.

According to business records, Lee and Heng started a cleaning company called Plus Concept in 1999. But the company was terminated in 2001.

A neighbour, who wanted to be known only as Ms Chu, said she recalled seeing the two men move cleaning equipment such as brooms and mops into a white car some years ago.

The two suspects have been remanded in police custody for further investigation. The case against them will be heard again on Jan 17.

Madam Ng, the mother of the Sheng Siong supermarket chain CEO, was kidnapped on Wednesday. She was released on Thursday after a $2 million ransom was paid. The two men were arrested later.

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