The main difference between Neice and Niece is that the Neice is a misspelling of niece and Niece is a A relative, in general; especially, a descendant, whether male or female; a granddaughter or a grandson.
In the language of kinship, a nephew is a son of a person's sibling, and a niece is a daughter of a person's sibling. Conversely, that person is the aunt or uncle of their niece or nephew. The relationship of aunt/uncle to niece/nephew is an example of second-degree relatives, meaning that their coefficient of relationship is 25%. The terms are also used colloquially for sons and daughters of siblings-in-law, even though there is no blood relationship.
misspelling of niece
A daughter of one’s sibling, brother-in-law, or sister-in-law; either the daughter of one's brother ("fraternal niece"), or of one's sister ("sororal niece").
"My niece just celebrated her 15th birthday."
A relative, in general; especially, a descendant, whether male or female; a granddaughter or a grandson.
A daughter of one's brother or sister, or of one's brother-in-law or sister-in-law. In modern English, this is the primary meaning.
a daughter of your brother or sister