Marriage contract
A marriage contract was an agreement to be married to someone for a set period of time. In Ferengi law, five year marriage contracts were standard, and the agreement was signed with the father of the female party.
Rom signed one of these contracts with his wife Prinadora's father because he wished to have a child. He fell in love with his wife, and wished to extend the contract. Her father used the extension to swindle money from Rom, she left him for a richer man, and poor Rom was left with Nog.
Quark reminded Rom of his failed marriage in 2373 when the younger Ferengi was considering a long-term relationship with Leeta. (DS9: "Doctor Bashir, I Presume")