cousin marriage

Not many countries in the world permit marriage between cousins. One day I was teaching the grammar "may" and asked my students, "May you marry your cousin in your country?" Then, all of them said strongly, "Never!! It is not allowed," "If you marry your cousin, children between them will be not in good health!" and "Cousins are family! How can you get married!?" But actually, it is possible in Japan. Listening to their strong opposition, a mischievous idea came up to me. I said to them, "Well, in fact, my husband is my cousin." Then the class froze with surprise. All of the students looked at me and became silent. That was very funny. When I said, "It's a lie", they laughed with relief.