A Singaporean mum who lost a 2011 court tussle to keep her twin sons here but persisted in her custody struggles in the United States has been handed a US court order to have the boys placed in her California home and away from their American father.

This new twist surfaced in judgment grounds issued by the Singapore High Court on Monday, after she lost a court battle for ownership of a $2 million condo unit here registered in the couple's joint names in 2001. The ex-husband was awarded sole beneficial ownership.

Judicial Commissioner Foo Tuat Yien noted from information given that in March this year, "the USA Juvenile Court ordered that the twins be placed in (her) home under the supervision of the relevant child authority with a report to be furnished to the court before the next hearing fixed for Aug 31, 2017. (He) was not granted visitation rights."

The Singaporean, 52 this year, has been embroiled with her former American husband in a custody spat for her boys, now 17.

The twins had been living with the father since they returned to the US, on a family court order in 2011.

The couple split in 2009 in the US after a near 10-year union. But the marriage was declared void there as it emerged that her divorce to her first husband, whose details were not provided, had not been completed when she married the American in 1999.

In 2009, while there were still unresolved access and custody issues before the US courts, the mother left Los Angeles with the boys and returned to Singapore, where the boys remained for about 18 months.

In December 2009, based on a DNA test, a Singapore court recorded an order which showed the American was not the biological father of the twins. An ex-colleague who was the natural father had disclaimed any interest as a parent.

But the American succeeded in court action here to take them back to the US as the family court ruled custody matters had to be settled in the US court.

The twins have been living with him in California until recently. Their mother, who is living in the US, had weekly visitation rights.

The property tussle involved a condo unit in Singapore bought by the American in 1997 and transferred to her in 2001 to be held as joint tenants.

At the four-day High Court hearing last year, the American was represented by lawyer A. Alagappan and the woman by lawyers June Lim and Low Seow Ling.

Judicial Commissioner Foo, noting that the parties never lived in the property, said prior statements and documents during matrimonial proceedings in the US showed both parties "had a common intention that (he) would be the sole beneficial owner of the property".

The judge was also not convinced that the sale of the woman's Housing Board flat in 2000 or her alleged contributions to household expenses would entitle her to a beneficial interest in the property by way of a constructive trust.

Judicial Commissioner Foo ruled that the American beneficially owned the property and dismissed the woman's claim to a half-share.

"It is unfortunate that the marriage was invalid, and as such, annulled. Flowing from this are certain consequences, many of which could or did cause hardship to the parties. (She) may have made sacrifices in her relationship with (him).

"However, these are not matters of which property law is well-suited to take cognisance," said Judicial Commissioner Foo.