When one's sibling has a daughter with their parent, the child becomes their niester; a niece because they're their sibling's daughter, and a sister being their parent's daughter, making her a niester.
My niester Ruby is so hot, I just might have to date her and take her to prom this year.
An unusual possibility of someone whom is a niece and a sister at the same time; capable of occuring when a woman has a child with a father and another with his son, or when a man produces children with a mother and a daughter, the niester being the result of the one person and the younger generation (having the child with the son or daughter) as related to the other child.
Family reunion this weekend! I can't wait to see Colleen, whom is my niester. What's a niester you may be asking yourself? Well, my Dad had a kid with my sister, which makes her my sister and my niece at the same time. Yeah, I know, we're a bunch of rednecks.