Couple, pair, brace, yoke are comparable when meaning two things of the same kind.
Couple applies to two things of the same sort, regarded as in some way associated, but not necessarily (except in the case of a married or mated pair) matched or belonging together; it frequently means no more than two.
Pair applies to two things that belong or are used together, frequently so that one is useless or defective without the other; it also applies to a single object (as trousers, spectacles, scissors, or tongs) composed of two corresponding or complementary parts.
Brace applies especially to a couple of certain animals or occasionally, to a couple of inanimate objects or rarely and usually with contemptuous connotations to persons.
Yoke applies to two animals linked together. It is used of persons only in contempt.