 Through the secret Mutual Pact of Succession ("Pactum Mutuae Successionis") of 1703, signed by both Joseph I and Charles VI with the knowledge and consent of their father, was determined that if both brothers died without surviving male issue, the daughters of the elder brother (Joseph) would have absolute precedence over the daughters of the younger brother (Charles) and the eldest daughter of Joseph would ascend all the Habsburg thrones.In the case that both brothers died without surviving issue, their surviving sisters would be the heiresses.This secret pact was only known to Leopold I, his sons and Baron Seliern