Nephew or nephew-in-law

In my experience, one refers to a parent's sibling's spouse "uncle" or "aunt". One would say, "this is my aunt Mary", even were she married to my mother's brother rather than being my mother's sister. Does this also extend to siblings children's spouses? Do I say "my nephew" for my brother's daughter's husband? I saw "nephew-in-law" on the web, but I have never heard it spoken. What is correct?