Q. All senses must be engaged in the devotional service of Krishna. Kindly inform how the desire of Sex of a human being, can be put into the service of Krishna? – Krishna says in bhagavad gita…(7.11)
A. “I am the strength of the strong, devoid of passion and desire. I am sex life which is not contrary to religious principles, O lord of the Bharatas [Arjuna]”.
PURPORT by Srila Prabhupada-
The strong man’s strength should be applied to protect the weak, not for personal aggression. Similarly, sex life, according to religious principles (dharma), should be for the propagation of children, not otherwise. The responsibility of parents is then to make their offspring Krishna conscious.