The son of a brother or a sister, or of a brother-in-law or sister-in-law.
A grandson or grandchild, or remoter lineal descendant.
son of one's brother or sister or brother- or sister-in-law. (archaic) grandson
This term has practically the same usage as in modsern times, except in very old records, it could also mean niece. In Middle English it meant grandson or granddaughter.
Until the end of the 1600â€™s, this meant a Grandson, descendant, or kinsman.
a son of your brother or sister
the son of a person's brother or sister.
son of one's brother or sister; also an illegitimate son of an eccleasiastic, a niece, or a male or female grandchild