In the Book of Genesis, Laban is the brother of Rebekah and the father of Leah and Rachel. As such he is brother-in-law to Isaac and twice the father-in-law to Jacob.
Laban first appears in the story in Genesis 24:29-60, where he is impressed by the gold jewelery given to his sister on behalf of Isaac, and plays a key part in arranging their marriage.
Much later, Laban promises his younger daughter Rachel to Jacob (Rebekah's son) in return for seven years' service, only to trick him into marrying his elder daughter Leah instead. Jacob then serves another seven years in exchange for the right to also marry his choice, Rachel, see Genesis 29.
Laban's flocks and fortunes increase under Jacob's skilled care, but there is much further trickery between them. Six years after his promised service has ended, Jacob, having prospered largely by proving more cunning than his father-in-law, finally leaves. Laban pursues him, but they eventually part on good terms, see Genesis 31.