There was an eight year difference between Cleopatra and her younger brother Ptolemy XIII; Cleopatra was 18 and Ptolemy XIII was 10 when the throne was given to both of them. Having already ruled with her father, Cleopatra was not keen on co-ruling with her brother, and began to usurp his authority - https://legioilynx.com/2016/12/12/cleopatra-becoming-a-femal...

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Poland

Hedwig (ruled 1384–1399) - she was crowned as King of Poland to emphasize that she was a monarch in her own right; she co-ruled with her husband Władysław II Jagiełło from 1386

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Kingdom of Ireland

Mary II (ruled 1689-1694) - she co-ruled with her husband William of Orange

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Sicily

Constance I (ruled 1194–1198) - she co-ruled with her husband Henry of Hohenstaufen until 1197
Constance II (ruled 1282–1285) - she co-ruled with her husband Peter III of Aragon
Maria (ruled 1377–1401) - she co-ruled with her husband Martin I the Younger from 1392

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Crusader Kingdom of Jerusalem

Melisende (ruled 1131–1153) - she ruled with her husband Fulk of Anjou then with her son Baldwin III as co-rulers
Sibylla (ruled 1186–1190) - she ruled with her husband Guy de Lusignan as co-ruler
Isabella I (ruled 1190/92–1205) - she ruled with her husbands Conrad of Montferrat, Henry of Champagne and Aimery of Cyprus as co-rulers
Maria (ruled 1205–1212) - she ruled with her husband John of Brienne as co-ruler from 1210
Isabella II (ruled 1212–1228), also known as Yolande of Jerusalem - she ruled with her husband Frederick II of Hohenstaufen as co-ruler from 1225

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Armenian Kingdom of Cilicia

Isabella (ruled 1219–1252) - she co-ruled with her husband Hethum I from 1226


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Sulayhid dynasty

Asma bint Shihab (ruled 1047-1087) - she was the co-ruler of Yemen in co-regency with her cousin and spouse, Ali al-Sulayhi, and later her son, Ahmad al-Mukkaram, and daughter-in-law, Arwa al-Sulayhi.

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Odrysian kingdom
Antonia Tryphaena (ruled 18–38), co-ruling with Rhoemetalces II, son of Raskouporis II
Pythodoris II (ruled 38–46), co-ruling with Rhoemetalces III, son of Cotys