I know that is possible...The Netherlands does it...Spanish aristocratic families do it as well...most recently the Duke of Huéscar who is a Fitzjames-Stuart and not a Martínez de Irujo likehis siblings.
However, for me a dynasty ends when the male line loses the throne and given who royals marry these days, chances are dear, lovable, darling little Leonor will end up marrying someone just as commoner as her mommy. Hurrah then we will say to the new dynasty of Perez, Rodriguez, Campos, Gonzalez or something equally common-sounding. Then again I most likely will not live long enough to see that debacle.
Arturo Beéche