An "in-law" is a term that refers to the relatives of one's spouse or partner. In the context of porn videos, the term "in-law" could mean different things:
1. A scene where characters are having sexual relations with their spouse's family members, breaking societal norms and boundaries. This can be considered as taboo content.
2. A scene that involves characters who share a familial relationship with each other through marriage but do not engage in sexual activities together due to their respective relationships with the actual partners.
3. A scene where characters are engaging in roleplay around family dynamics, which includes pretending to be in-laws, perhaps in an attempt to explore dominant/submissive or authority/submission dynamics.