Did any European monarch execute their sister or other direct female relative?

Question

In my search, I found examples of kings/queens having their wives and brothers executed, but I cannot seem to locate any example for sisters, mothers, and fathers.

Answer 1

Most historical examples of European Monarchs executing their immediate family were motivated by the customs used to determine succession to the throne. Primogeniture stipulated that the first- born male offspring was to succeed to the throne; unless of course, circumstances like death kept them from maintaining the throne. In which case, the crown would go to the next eldest male offspring. The system caused bitter rivalries between brothers in many royal families as they all had potential claims to the throne.

Many monarchs were aware of the potential threat that their brothers posed under the system of primogeniture and had them executed.

In case the of wives, the execution was usually because she had been found guilty of treason. Accusations of treason could result from many different situations. Mostly, the wife would be executed if political relations had gone sour between the monarch and her family. Sisters and mothers were generally not considered to be a threat as they were not historically seen as successors to the throne.