Coalition size and kinship.
When coalitions are small, each male in the coalition has about equal reproductive success.
When coalitions are large, some individuals have very low reproductive success, and their main benefit in joining the coalition is to promote the reproduction of their kin, thus large coalitions are more likely to be made up of kin, providing an indirect benefit to those males that do not father their own cubs.

The numbers by each point indicate the number of cubs fathered by each male in that coalition, and a box around the number indicates that the males are close relatives.