Batak Toba Pariban(If you're a man), women with the same surname as your mother. (If you're a women), men whose mothers' surname is the same as yours. Has an added implication of being the best pairings for marriage.

Basically, for Batak people, if you want to marry it's vest to marry your Pariban. Also, several surnames (marga) can be considered the same marga family, as they were descended from a common ancestor. You may note that cousins might be called Pariban. Yes, the term actually means a specific type of cousin, and the "best" Pariban to marry is your own cousin. No one does that anymore, though. Small interesting thing : only men can recognize who their Pariban is at first, since you don't usually know surnames of other people mothers.