For Gloria married his wife's father, widower Jim Brindle.
And right away that made sister Gloria Harry's mother-in-law. By the same token, Wendy's father also became her own brother-in-law. Now Wendy wonders whether her husband is also he Uncle Harry. After all, she is the daughter of the man who married her husband's sister!
As Harry, of South Preston, Lancashire, put it: "I've even worked out that sister Gloria is her own mother-in-law – I think..."