Many saintly persons and sages like Nārada Muni used to visit the palace of King Bhīṣmaka. Naturally Rukmiṇī had a chance to talk with them, and in this way she obtained information about Kṛṣṇa. She was informed about the six opulences of Kṛṣṇa, and simply by hearing about Him she desired to surrender herself to His lotus feet and become His wife. Kṛṣṇa had also heard of Rukmiṇī. She was the reservoir of all transcendental qualities: intelligence, auspicious physical features, liberal-mindedness, exquisite beauty and righteous behavior. Kṛṣṇa therefore decided that she was fit to be His wife. All of the relatives of King Bhīṣmaka decided that Rukmiṇī should be given in marriage to Kṛṣṇa. But her elder brother Rukmī, despite the desire of the others, arranged for her marriage with Śiśupāla, a determined enemy of Kṛṣṇa. When the black-eyed, beautiful Rukmiṇī heard of the settlement, she immediately became very morose. However, being a king's daughter, she understood political diplomacy and decided that there was no use in simply being morose. Some steps should be taken immediately. After some deliberation, she decided to send a message to Kṛṣṇa, and so that she might not be deceived, she selected a qualified brāhmaṇa as her messenger. Such a qualified brāhmaṇa is always truthful and is a devotee of Viṣṇu. Without delay, she sent the brāhmaṇa to Dvārakā.
All of the relatives of King Bhismaka decided that Rukmini should be given in marriage to Krsna. But her elder brother Rukmi, despite the desire of the others, arranged for her marriage with Sisupala
SB Cantos 10.14 to 12 (Translations Only)
Because Rukmī envied the Lord, O King, he forbade his family members to give his sister to Kṛṣṇa, although they wanted to. Instead, Rukmī decided to give Rukmiṇī to Śiśupāla.
Other Books by Srila Prabhupada
Krsna, The Supreme Personality of Godhead
When King Bhīṣmaka learned that Damaghoṣa and his party were arriving, he left the city to receive them. Outside the city gate were many gardens where guests were welcome to stay. In the Vedic system of marriage, the bride's father receives the large party of the bridegroom and accommodates them in a suitable place for two or three days until the marriage ceremony is performed. The party led by Damaghoṣa contained thousands of men, among whom the prominent kings and personalities were Jarāsandha, Dantavakra, Vidūratha and Pauṇḍraka. It was an open secret that Rukmiṇī was meant to be married to Kṛṣṇa but that her elder brother Rukmī had arranged her marriage to Śiśupāla. There was also some whispering about a rumor that Rukmiṇī had sent a messenger to Kṛṣṇa; therefore the soldiers suspected that Kṛṣṇa might cause a disturbance by attempting to kidnap Rukmiṇī. Even though they were not without fear, they were all prepared to give Kṛṣṇa a good fight to prevent the girl from being taken away. Śrī Balarāma received the news that Kṛṣṇa had left for Kuṇḍina accompanied only by a brāhmaṇa and that Śiśupāla was there with a large number of soldiers. Balarāma suspected that they would attack Kṛṣṇa, and thus out of great affection for His brother He took strong military divisions of chariots, infantry, horses and elephants and went to the precincts of Kuṇḍina.