We work with birth at our level through transmutation, whether married or single, since both produce the birth of virtues, qualities, principles, essences, soul, and cognizance, yet at different levels.
Comprehension and death of the ego, as well as selfless service to humanity, are factors inseparable from birth. You cannot isolate the three factors from each other.
You cannot enter into the minor initiations without working with birth, even if it is at the level of a minor brother or sister (working in the initiations of minor mysteries). This is because one gives birth to virtues through scientific chastity, whether single or married.
The question, however, is the degree to which one can attain spiritual birth. Obviously one must be married to enter into the Major Mysteries, yet one cannot progress anywhere without working with birth: transmutation, whether single or married.
When the ego dies, the soul is born. Individual practitioners can annihilate up to fifty percent of their defects and give birth to fifty percent of liberated essence. To attain more requires marriage.
For thirty years I sought God. But when I looked carefully I found that in reality God was the seeker and I the sought. -Bayazid al-Bastami