The principle is that when one becomes a grhastha, he must live perfectly in that order, which means he must live peacefully with a wife and children
SB Canto 5
Thereafter, Mahārāja Priyavrata married Barhiṣmatī, the daughter of the prajāpati named Viśvakarmā. In her he begot ten sons equal to him in beauty, character, magnanimity and other qualities. He also begot a daughter, the youngest of all, named Ūrjasvatī.
Mahārāja Priyavrata not only carried out the order of Lord Brahmā by accepting the duties of government, but also married Barhiṣmatī, the daughter of Viśvakarmā, one of the prajāpatis. Since Mahārāja Priyavrata was fully trained in transcendental knowledge, he could have returned home and conducted the business of government as a brahmacārī. Instead, however, when he returned to household life, he accepted a wife also. The principle is that when one becomes a gṛhastha, he must live perfectly in that order, which means he must live peacefully with a wife and children. When Caitanya Mahāprabhu's first wife died, His mother requested Him to marry for a second time. He was twenty years old and was going to take sannyāsa at the age of twenty-four, yet by the request of His mother, He married. "As long as I am in household life," He told His mother, "I must have a wife, for household life does not mean staying in a house. Real household life means living in a house with a wife."
Three words in this verse are very significant—u ha vāva. These words are used to express wonder. Priyavrata Mahārāja had taken a vow of renunciation, but accepting a wife and begetting children have nothing to do with the path of renunciation; these are activities on the path of enjoyment. It was a source of great wonder, therefore, that Priyavrata Mahārāja, who had followed the path of renunciation, had now accepted the path of enjoyment.
Sometimes we are criticized because although I am a sannyāsī, I have taken part in the marriage ceremonies of my disciples. It must be explained, however, that since we have started a Kṛṣṇa conscious society and since a human society must also have ideal marriages, to correctly establish an ideal society we must take part in marrying some of its members, although we have taken to the path of renunciation. This may be astonishing to persons who are not very interested in establishing daiva-varṇāśrama, the transcendental system of four social orders and four spiritual orders. Śrīla Bhaktisiddhānta Sarasvatī Ṭhākura, however, wanted to reestablish daiva-varṇāśrama. In daiva-varṇāśrama there cannot be acknowledgement of social status according to birthright because in Bhagavad-gītā it is said that the determining considerations are guṇa and karma, one's qualities and work. It is this daiva-varṇāśrama that should be established all over the world to continue a perfect society for Kṛṣṇa consciousness. This may be astonishing to foolish critics, but it is one of the functions of a Kṛṣṇa conscious society.