They belong all to the subfamily Alcelaphinae which have the sloping profile and horns in boths sexes.

They are very similar, the horns are more or less open and come in slightly different shapes, some species are larger and the colouration is different.
The closest relatives of the Tssessebe are Blesbok and Bontebok (all members of the genus
Damaliscus)

(The Behavior Guide to African Mammals. Richard Estes)