In the High Court in Johannesburg, Judge Halima Salduker ruled earlier this week that grandparents had a legal obligation to support their grandchildren.

The foster-child grant, worth R770, is available under the Children's Act for children abandoned or orphaned and without any visible means of support.

Without the foster-child grant, grandmothers would have to rely on the R280 child-support grant.

Salduker ruled biological parents, adoptive parents and adult siblings had a "duty of support" to look after the child.

But aunts and uncles were eligible for foster-child grants because they did not have the same obligation, according to Sunday Times reporters.

The judgement was the result of an appeal by the Centre for Child Law at the University of Pretoria against a ruling by the Krugersdorp Children's Court.

The centre had appealed after a great-aunt caring for a 12-year-old boy was turned down for a child support grant.

Salduker's ruling was binding on all Children's Courts in Gauteng, and could set a precedent for the rest of the country, according to the paper.