Inter-caste marriage (or other relationships) in caste societies like India is an example of a relationship between two imbalanced parties that is taboo as it challenges the caste system. Contrast them to inter-class relationships, which are much more accepted. They have been gaining acceptance in India.
Furthermore, people from lower castes may be victimised by people from upper castes.
So I just wanted to bring this analogy to the table, although one difference to inter-generational relationships is that no one considers inter-caste relationships to be abusive (as far as I'm aware). Rather, both partners will suffer stigma.