This story comes from the Mahabharata and Bhagavata Purana. This is a cousin marriage. Arjuna’s mother and Subhadra’s father are siblings. Many communities in India forbid marriages between sa-pinda (common grandfathers, great grandfathers) and between sa-gotra (same clan). While North Indians forbid marriage between cousins, it is common in South India, especially in land-owning families, to ensure the land remains in the extended family.
