At the age of 59 Frederick married for a third time: the widow Sophie Sybille von Leiningen-Westerburg, a connection of his mother's family, who bore him three more children.
La vârsta de 59 de ani, Frederic s-a căsătorit a treia oară: cu văduva Sofia Sybille von Leiningen-Westerburg, o rudă a familiei mamei sale, care i-a mai dăruit încă trei copii.