Hinduism religion is primarily divided into two parts religious and spiritual. Not much importance is accorded to religious path (indulgence in rituals) for it never leads to god. All Hinduism scriptures like Bhagavad Gita and Upanishads (independent spiritual treatises) primarily dealt with subject of spirituality, the path that directly led to god, self realization, enlightenment.
For both the paths religious and spiritual a physical relationship outside the fold of marriage was prohibited. As per Hinduism scriptures the physical relationship was primarily meant for progeny, never lust or mindless sexual indulgence.
For travelers of spiritual path abstention from sexual indulgence in totality was recommended. For practicing celibacy, Brahmacharya Vrata no physical relationships of any kind were permitted. For becoming a Swami Vivekananda and finally Sri Ramakrishna Paramhansa practice of absolute celibacy gets necessitated. Such a seeker finally sees only three relationships with womenfolk, that of mother, sister or daughter. There never was a fourth relationship.
It is because of such high standards of non-indulgence in sex, seekers in Hinduism finally succeed reaching stage of Mahavira, Gautama Buddha, Sri Ramakrishna Paramhansa and Maharshi Ramana.
For those practicing religion, practicing physical relationship within the family fold was the norm. Extramarital relationships had no place in Hinduism. Even though Kama Sutra by Vatsyayana relates to Hinduism, it only depicts love in its purest form.