Your interpretation of the parts are mostly correct, but the final translation doesn't seem right. Firstly, the phrase is not a full sentence but just a noun phrase. It means "The reason why it won't do if it's not you even if I'm born again", or "The reason why no one would do except you even if I had to do it over again". It doesn't have the sense of "I won't have a reason for being born again" appearing in your translation. We'd have to add the subject or predicate to make a complete sentence, for example: - 그것이 [다시 태어난대도 ... 안 될 이유]이다. That is the reason why it won't do ... - [다시 태어난대도 ... 안 될 이유]는 이거야. The reason why it won't do ... is this. In song lyrics, what comes before or after the line may fill in as the subject or the predicate. As for ~ㄹ in 안 될 이유, it can mean the future as well as an expectation or obligation, depending on how it's used. ~ㄹ is similar to the to-infinitive in English, which may, but doesn't always mean explicit future tense. For example: - 갈 사람 = someone to leave, or someone who will leave (future or expectation). - 할 일 = work to do (obligation). - 일어날 일 = things to happen, things to come, or things that will happen (future or expectation).