Abendanon, 25, has already joined the squad ahead of the second Test against the Springboks on Saturday in Johannesburg, where he attended the weekend wedding of Bath team mate Pieter Dixon.
South Africa lost their full-back Zane Kirchner on Monday for the second Test. Kirchner injured his knee in the first Test in Durban last weekend and will be replaced by Stormers utility back Gio Aplon.
Abendanon was born in Johannesburg and made his Test debut in Pretoria against the Springboks in 2007. He won his second and last Test cap against France at Twickenham later that year. Brown will return home for an operation on his thumb.
England's backline will have to be further shuffled for the second Test after centre Brad Barritt, another South African-born player, underwent a minor operation at the weekend for a lacerated eyeball.
"Barritt won't figure in this week's games, but will join us in Johannesburg later this week," England media manager Dave Barton said.
South Africa, who staged a second-half rally to beat England 22-17 in the first Test last Saturday, said Kirchner's knee would be checked again next week ahead of the final Test in Port Elizabeth on June 23.
"It's always tough losing a full-back because it means you need a specialist reserve," Springbok coach Heyneke Meyer said.
England play a Southern Barbarians XV in Kimberley on Wednesday before flying back for the second Test and coach Stuart Lancaster said the midweek match would provide an opportunity for him to build some midfield depth.
"I'm playing what would be regarded as two specialist 12s on Wednesday because I want to look at Anthony Allen at 13," Lancaster said.
"The plan is that Anthony will move to 12 in the second half and George Lowe will come on at outside centre. It's about creating opportunities for everyone and not pigeonholing them," said.
"We must have options in different positions and you don't get the opportunity to work on that in international rugby - there's no pre-season and very few warm-up matches," he added.