The first is incorrect. When using past perfect you must always use "have" in simple past and the verb in "past participle".

"Broke" is the past tense form of "to break." "Broken" is the past participle. Therefore, "they had broken" is the only correct way to write it. Occasionally, you'll hear native English speakers saying things like "his arm had broke" or "they have broke up," but that's incorrect.

''they had broke '' that sentence is false..Because empty of meaning sentence ''they had broken'' that sentence is true.Because describes a situation in the past