Cleopatra VII (69 BC – 30 BC) and Ptolemy XIII (62/61 BC – 47 BC)

Cleopatra married her brother, Ptolemy XIII. She was 18 years old and he was 10 years old at the time. They married in keeping with the Egyptian tradition and served as co-regents.

Not only were they far from affectionate toward each other, they actually fought a civil war against each other, attempting to claim sole right to the throne.

She later married another brother, Ptolemy XIV.

source