Thank you for your good question!
According to Sakar Murlis, Krishna will be born as destruction takes place. As we know, there is not much mentioned about Krishna’s parents; other than belonging to royalty. We also know about the “Advanced Party.” Personally, I do not want to speculate as far as how Krishna is born. The only thing I know for a fact, is that a different consciousness has to give him birth. Human beings are not aware of that consciousness at this time, for we are floating in the vices.
Celibacy in Brahmin souls at this time is required not because “sex is bad;” but because we have vices in us which will degrade us and which are “running the show in our lives.” A Brahmin soul has the potential to follow celibacy in a numberwise way. For, being able to be celibate in a healthy way, without repression; is the trademark of being liberated from sex lust. Until we have not been liberated from that vice, we will not be able to understand the “how that happens” on spiritually advanced beings. 🙂