であれ / であろうと

であれ and であろうと mean "whatever it is", "even if it is": the statement after them holds whatever fills the slot. Both go straight after a noun or a な-adjective, most often one built on a question word – なん何であれ, だれ誰であろうと.

The two forms mean the same, and both are formal and written. In speech, use でも or だろうと: りゆう理由がなん何でも, だれ誰だろうと.

Even if it is X

Without a question word, the clause concedes a single case: "even if it is X", "even X". たとえ often comes in front and makes the concession plain.

AであれBであれ

Repeated after two nouns, either form means "whether A or B". The repeated pattern has its own grammar point, であれ～であれ.

であれ is the command form of である and であろう its volitional form, but neither gives a command or a guess here. であっても is close in meaning and a step less formal.