Sentence:  Between uncle and aunt-in-law, or uncle's wife, you have a connection of affinity, and you have the same between aunt and <WSD>uncle-in-law</WSD>, or aunt's wife. "[sic]" <!-- Since this is an 1871 quote, this should have been aunt's husband rather than an implicit endorsement of same-sex marriage. --> 
Meaning of the word marked with <WSD> tags:  The husband of one's uncle or aunt (parent's sibling).