Okay, that's a possible tangle, but let's look at the possibilities.
1) Your aunt is not a blood relation at all, but is what we would call an "aunt by marriage." This is the most usual scenario, and yes, their children would be your first cousins, but the aunt is really a courtesy title, and bears no actual relationship to you.
2) The second scenario is more problematic because it would seem to indicate a marriage between siblings; your husband's uncle and aunt marrying, which would, of course, mean that the uncle married his own sister. That would not be legal, just as first cousins are not allowed to marry.
3) The other possibility is that your aunt could have been the aunt of your mother, making her your grand aunt. If the two families were acquainted back then, then yes, you would have this sort of situation arise, and that aunt would also be a blood relation to you.
I know that I ran into a weird situation in my own family history, in which the same set of parents showed up on both the mother's and father's side of the family. This resulted in a mother being a second cousin once removed from her own child!
That apparently happened a fair amount back in the 1700s, because people were not nearly as mobile as we are today; they were generally born and lived out their lives within about a 50-mile radius. After a time, they ran out of people to marry besides their cousins! (2nd cousins and further distant are allowed to marry each other.)
I hope this helps you figure out your puzzle. The best thing to do, if these family members are still living, is to interview them and ask directly what the story is.