Villains who are relatives of one of the main protagonists be they Parents, Siblings, Spouses, or children.

This is a common trend in fiction in an attempt to add drama and to a lesser extent, irony to the story. Indeed, having to fight a close relative is a source of much inner turmoil to the hero who cannot reconcile their quest and familial ties. Often, this results in the villain attempting to turn the hero over to their side. Other times, the opposite will occur and the hero will attempt to turn the villain back to their side which can eventually lead to redemption. However some hero-related villains can be Complete Monsters if they have no affection and feeling of love towards the heroes while meeting all the criteria (e.g. Kanade Otonokoji, Mari, and Xochtal Reklaw)