Spider Family

Spider Family is a supporting antagonistic faction in Kimetsu no Yaiba and Arc Villains of Natagumo Mountain Arc. Formed by Rui, the Lower Moon Five and one of the Twelve Demon Moons, the Spider Family is a clan form by spider demons that were once human.

Overview
The Spider Family was a fabricated family of demons made once Rui was transformed into a demon and became the Lower Moon Five by Muzan Kibutsuji. It was formed due to Rui's tramatic experience of forcibly killing his family in defense, and out of Rui's desire to create a family of his own. Rui developed the family by luring humans into the mountain and turned them into spiders with the spider demons' blood.

Though it was called "family", the Spider Family has little to no familial feelings towards each other, with Rui as the true leader who will punish the weak members of his "family" the female members being abused by the male, and Rui will scare and punish anyone who failed to follow their duty.

In fact, Rui's point of view in family bond was very childish, extreme and biased, believing a family meant domination over others and adding terror upon them. He also had no hestitation to punish others either when they accidentally transformed back into human beings or tried to escape. The other members were either too weak or too cowardly to defy Rui.

In a nutshell, Rui's family was combined by a fabricated bond full of double standards, since they claimed they wanted to shield their family members from outsiders but had no problem adding domestic abuse or even murder upon them.

The Spider Family met their downfall during their attack against the Demon Slaying Corps. Although killing countless of the Corp's lesser members, the Spider Family members later met their defeat at the hands of Tanjiro and his close ones, before being finished off by Shinobu Kocho and Giyu Tomioka one at the time.

Trivia

 * The Spider Family are the only team of demons in the story besides Twelve Demon Moons.