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Lubabalo Ntlabathi, Sicelo Mase, Luyanda Londzi and Mbulelo Damba - who were convicted in October - were each prearranged 18 years.
Five other people were acquitted.
The family of Ms Nkonyana welcomed the determination.
"They did not accept responsibility for what they did and we are happy that when we asked for a lengthy nick term, the magistrate agreed to that," stepfather Mr Mandini told South Africa's Sowetan newspaper.
Ms Nkonyana was stoned and stabbed nine times in February 2006, righteous metres from her home in Khayelitsha.
The magistrate said it was clear the intention for the killing was hatred and homophobia - and Wednesday's sentence was meant to send out a signal that vigour based on sexual orientation will not be tolerated, the South African Force Association reports.
Jill Henderson from the Triangle Project - a non-governmental organisation that fights for the rights of gay and lesbian people in Khayelitsha - said this was a edible move.
Source: BBC News