How many letters does the top answer for “two items of the same kind” have?

The most common answer is distich (7 letters).

Crossword clue: two items of the same kind

4 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

distich 7 letters wn-def

two items of the same kind

duad 4 letters wn-def

two items of the same kind

dyad 4 letters wn-def

two items of the same kind

twain 5 letters wn-def

two items of the same kind

of the same kind 50% similar → suchlike