What is the ruling on marrying a widow seven years my senior, despite my family's refusal because she is from outside the tribe?

If "family" refers to the parents, then one must obey them in refraining from marrying a specific girl, unless there is a fear of falling into sin. Age difference or the absence of family does not affect the legitimacy of the marriage. The Prophet, peace and blessings be upon him, married Khadijah, may Allah be pleased with her, and she was older than him and a widow. Tribe, lineage, and ancestry are not essential criteria for choosing a wife. It is advised to try to convince the parents, but if they refuse, then one must obey them.