Sentence:  The youngest son of Frikkie's sister had been betrothed to the girl who had measles in my house ; she was my sister's child, and thus I was <WSD>double aunt</WSD>. 
Meaning of the word marked with <WSD> tags:  A woman who is one's aunt in two ways, e.g. being a sister of one parent and the wife of a sibling of the other.