ptolemy xii died sometime before 22 march 51 bc, the date of cleopatra's first known act as queen: her voyage to hermonthis, near thebes, to install a new sacred buchis bull (worshiped as an intermediary for the god montu in ancient egyptian religion). the roman senate was not informed about ptolemy's death until 30 june or 1 august 51 bc; the news may have been suppressed by cleopatra until she could secure the throne. cleopatra probably married her brother, ptolemy xiii, but the marriage is uncertain. the incestuous ptolemaic practice of sibling marriage was introduced by ptolemy ii and his sister, arsinoe ii, but the long-held royal egyptian practice was considered scandalous by contemporary greeks. although vocal critics of this incestuous practice were sometimes violently punished and suppressed during the joint reign of ptolemy ii and arsinoe ii, sibling marriages were nevertheless considered a normal arrangement for ptolemaic rulers by the time of cleopatra's reign. official documents began listing cleopatra as sole ruler by 29 august 51 bc, evidence that she had rejected her brother as a co-ruler.