The South African Rugby Union (SARU) confirmed earlier this month that the two clubs would be cut from Super Rugby, which spans New Zealand, Japan and Argentina, as well as South Africa.
UK public-service broadcaster the BBC said that the teams have signed a six-year deal, which would land Pro12 an extra £6m (€6.8m/$7.8m) per season from SARU and extra television rights income.
The report added that the new ‘Pro14’ league would begin in September and be made up of two seven-team conferences. Each conference would feature one Scottish club, one South African team, one Italian side and two each from Wales and Ireland.
The clubs will play each of the teams in their mini-league twice over the course of the season, and each team in the other conference once. Two more games would be set aside as derby fixtures, creating a 21-game season.
The respective winners of the two conferences will qualify for the semi-finals, with second and third-place teams to meet in a play-off to determine the two remaining semi-final spots.