Intercaste marriage was current even in the olden days.

“Only by God’s grace can one get a nice wife just as he desires. Similarly, it is only by God’s grace that a girl gets a husband suitable to her heart. Thus it is said that if we pray to the Supreme Lord in every transaction of our material existence, everything will be done very nicely and just suitable to our heart’s desire. In other words, in all circumstances, we must take shelter of the Supreme Personality of Godhead and depend completely on His decision. Man proposes God disposes. The fulfillment of desires, therefore, should be entrusted to the Supreme Personality of Godhead that is the nicest solution. Kardama Muni desired only a wife, but because he was a devotee of the Lord, the Lord selected a wife for him who was the Emperor’s daughter, a princess. Thus Kardama Muni got a wife beyond his expectation. If we depend on the choice of the Supreme Personality of Godhead, we will receive benedictions in greater opulence than we desire. It is also significantly noted here that Kardama Muni was a brahmana, whereas Emperor Svayambhuva was a Kshatriya. Therefore, intercaste marriage was current even in those days. The system was that a brahmana could marry the daughter of a Kshatriya, but a Kshatriya could not marry the daughter of a brahmana. We have evidence from the history of the Vedic age that Sukracarya offered his daughter to Maharaja Yayati, but the King had to refuse to marry the daughter of a brahmana only with the special permission of the brahmana could they marry. Intercaste marriage, therefore, was not prohibited in the olden days, many millions of years ago, but there was a regular system of social behavior.”

Source: A.C. Bhaktivedanta Swami Prabhupada (2014 edition), “Srimad Bhagavatam”, Third Canto, Chapter 21 – Text 28