YOU SAID:

if you marry your uncle and have his child, wouldnt he be your cousin?

INTO JAPANESE

あなたがあなたの叔父と結婚し、彼の子供を持っているなら、彼はあなたのいとこではないでしょうか？

BACK INTO ENGLISH

If you marry your uncle and have his children, isn't he your cousin?

INTO JAPANESE

あなたの叔父と結婚し、彼の子供がいる場合、彼はあなたのいとこではありませんか？

BACK INTO ENGLISH

If you marry your uncle and have his children, isn't he your cousin?