|“||We share blood. But we are not brothers.||„|
|~ Noob Saibot to Sub-Zero.|
Evil Siblings are the type of villains who are related to the hero or heroine - brother or sister. In many stories bad siblings (most often older) bully, threaten, intimidate and abuse physically and mentally over the good sibling considering him/her worse. This type can also include half-siblings, step-siblings, and adoptive siblings.
In some other case, a bad sibling (younger or older) can be jealous of a good sibling who is loved and praised by his/her family.
For this purpose, he/she plans to get rid of good sibling, for example by killing him.
On the one hand, bad sibling in the past were loved to good sibling, but a some tragic or wrong event, may change him/her for the worse, blaming his/her own good sibling in result he/she have a huge resentment to hero/heroine.
Also villains have their own siblings, who helps in evil plans, but in other cases brother/sister of main villains serves as incompetent, bumbling and idiotic henchmen.