fellow men; between men; among men; man-to-man
fellow women; between women; among women; woman-to-woman
mankind; the human creature; fellow creatures
two people alike; two of a kind; kissing cousins; two people cut from the same cloth
friendly fire; killing each other by mistake; internecine strife
next-door neighbors; (living, sitting) next to each other
peers; friends; fellow workers; comrades
lovers; couple; soulmates; enthusiast; -aholic; -lover
one's fellow workers; fellow employees