The phrase "mismatched couple" refers to a pair of people in a romantic relationship who are noticeably different or incompatible in certain ways. Full definition
Others will be licentious bacchanals involving mismatched couples making bad decisions on piles of guests» coats. (chicagoparent.com)
The worn pages tell the story of young love between a socially mismatched couple (played by Rachel McAdams and Ryan Gosling). (parentpreviews.com)
If one partner has irresponsible spending habits that are unlikely to change or improve, a financially mismatched couple needs to see a credit counselor before they end up seeing a lawyer! (debthelp.com)