King Malayadhvaja was a great devotee, and after he married the daughter of King Vidarbha, he gave her one nice daughter, whose eyes were black. Figuratively this means that the daughter of King Malayadhvaja was also bestowed with devotional service, for her eyes were always fixed on Kṛṣṇa. A devotee has no vision in his life other than Kṛṣṇa. The seven sons are the seven processes of devotional service—hearing, chanting, remembering, offering worship, offering prayers, rendering transcendental loving service and serving the lotus feet of the Lord. Of the nine types of devotional service, only seven were immediately given. The balance—friendship and surrendering everything—were to be developed later. In other words, devotional service is divided into two categories—namely vidhi-mārga and rāga-mārga. The process of becoming friends with the Lord and sacrificing everything for Him belongs to the category of rāga-mārga, the stage of developed devotional service. For the neophyte, the important processes are those of hearing and chanting (śravaṇaṁ kīrtanam), remembering Kṛṣṇa, worshiping the Deity in the temple, offering prayers and always engaging in the service of the Lord, and worshiping the lotus feet of the Lord.
The word yavīyasaḥ indicates that these processes are very powerful. After a devotee engages in the processes of śravaṇaṁ kīrtanaṁ viṣṇoḥ smaraṇaṁ pāda-sevanam/ arcanaṁ vandanaṁ dāsyam (SB 7.5.23), and is able to secure these processes, he can later become a devotee capable of rendering spontaneous devotional service—namely sakhyam and ātma-nivedanam. Generally the great ācāryas who preach devotional service all over the world belong to the category of sakhyam ātma-nivedanam. A neophyte devotee cannot actually become a preacher. The neophyte is advised to execute devotional service in the seven other fields (śravaṇaṁ kīrtanam, etc.). If one can successfully execute the preliminary seven items, he can in the future be situated on the platform of sakhyam ātma-nivedanam.
The specific mention of Draviḍa-deśa refers to the five Draviḍa-deśas in South India. All are very strong in rendering the preliminary devotional processes (śravaṇaṁ kīrtanam (SB 7.5.23)). Some great ācāryas, like Rāmānujācārya and Madhvācārya, also came from Draviḍa-deśa and became great preachers. They were all situated on the platform of sakhyam ātma-nivedanam.