Complex sentence: It was not until June 1409 that the marriages were consummated, according to Jean Juvénal des Ursins, after which Margaret moved to the decadent court of her mother-in-law.
Split into simpler sentences: It was not until June 1409, however, that the marriages were consummated, according to Jean Juvénal des Ursins. Following the marriage, Margaret moved to the decadent court of her mother-in-law.