former is incorrectly written and it should be written as "ex-teammates" being its meaning: Ex, Latin preposition meaning denial among other things, could be applied to different words forming a semantic unit, although they do not exist as such in the dictionary of the RAE, to mean a reality that was but is no longer. A former partner is a partner who was but no longer; the same goes for former Minister, alumnus, former President and former seminarian... It is often applied to charges or passing situations.