Learn Farsi: تو باید به اینکه تبار تو نامعلوم است پی ببری. - You must realize the fact that your lineage is unknown.

The compound verb for 'to realize' or 'to find out' is pey bordan, which requires the preposition be. Because you are realizing an entire fact ('that your lineage is unknown'), you use in ke (the fact that) to act as a noun placeholder. The preposition be must attach to this placeholder, creating be in ke.

Normally, a long clause with in ke goes at the end of the sentence. Why is it in the middle here?

While long in ke clauses often get pushed to the end of a Farsi sentence, here it acts as the object of the preposition be before the final verb. Farsi grammar allows you to bracket the clause inside the main sentence structure: be in ke + [the clause] + [the conjugated verb pey bebari].

Why is the final verb pey bebari and not pey mibari?

The word bāyad (must) early in the sentence requires the main action to be in the subjunctive mood. For the compound verb pey bordan, you conjugate the bordan part into the present subjunctive for 'you' (singular), giving us bebari.

What is the literal translation of the compound verb pey bordan?