I agree with Patrish about the details on the 1881 but that doesn't stop them being your relatives. It looks as if they were very hopeful in refusing to age! The two sisters in the 1881 and 1891 are surely the same ones and their ages are 1881 - Ann 45, Catherine 40 and 1891 - Ann 44, Catherine 43!
By the 1901 it must have been impossible not to age otherwise "aunt" would only have been a few years older than her nephew and he would have know that wasn't right.
Other thoughts - in the 1891 Catherine doesn't give an occupation. I wonder if she was unwell/unable to work? Could she have gone back to Ireland? It's hard to understand the birthplace in 1881 being wrong - I'm willing to bet that both ladies would still have an unmistakable accent. My Irish relatives certainly did after a lifetime living in England.
Monica