ya virya-sulkena hrtah svayamvare
pramathya caidya-pramukhan hi susminah
yas cahrta bhauma-vadhe sahasrasah
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The children of these ladies are Pradyumna, Samba, Amba, etc. Ladies like Rukmini, Satyabhama and Jambavati were forcibly taken away by Him from their svayamvara ceremonies after He defeated many powerful kings, headed by Sisupala. And other ladies were also forcibly taken away by Him after He killed Bhaumasura and thousands of his assistants. All of these ladies are glorious.
Purport by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
Exceptionally qualified daughters of powerful kings were allowed to make a choice of their own bridegrooms in open competition, and such ceremonies were called svayamvara, or selection of the bridegroom. Because the svayamvara was an open competition between the rival and valiant princes, such princes were invited by the father of the princess, and usually there were regular fights between the invited princely order in a sporting spirit. But it so happened that sometimes the belligerent princes were killed in such marriage-fighting, and the victorious prince was offered the trophy princess for whom so many princes died. Rukmini, the principal queen of Lord Krsna, was the daughter of the King of Vidarbha, who wished that his qualified and beautiful daughter be given away to Lord Krsna. But her eldest brother wanted her to be given away to King Sisupala, who happened to be a cousin of Krsna. So there was open competition, and as usual Lord Krsna emerged successful, after harassing Sisupala and other princes by His unrivalled prowess. Rukmini had ten sons, like Pradyumna. There were other queens also taken away by Lord Krsna in a similar way. Full description of this beautiful booty of Lord Krsna will be given in the Tenth Canto. There were 16,100 beautiful girls who were daughters of many kings and were forcibly stolen by Bhaumasura, who kept them captive for his carnal desire. These girls prayed piteously to Lord Krsna for their deliverance, and the merciful Lord, called by their fervent prayer, released them all by fighting and killing Bhaumasura. All these captive princesses were then accepted by the Lord as His wives, although in the estimation of society they were all fallen girls. The all-powerful Lord Krsna accepted the humble prayers of these girls and married them with the adoration of queens. So altogether Lord Krsna had 16,108 queens at Dvaraka, and in each of them He begot ten children. All these children grew up, and each had as many children as the father. The aggregate of the family numbered in the millions.