What if the uncle/aunt is a woman younger than the nephew/niece? This is not far-fetched at all. If someone has a child at age 20 and another at age 42 and the older child also has a child at age 20 the nephew/niece will be the older of the two.
In any case, the father Joseph saw was over on embarrassing someone in public, which some poskim say is yehareg v’al yaavor. This is especially severe in the case of a child.