 The Franco-Monegasque Treaty of 1918 already provided that a childless sovereign of Monaco could adopt an heir to the throne.Therefore, had Rainier then chosen to adopt Christian de Massy, that would have made Christian the heir presumptive (although he would lose his place in the order of succession to any children born of a subsequent marriage of Rainier).Regardless, once Rainier married Grace Kelly and had children, Princess Antoinette's concern over succession waned and the possibility of Christian acceding to the throne became more remote.