Haakon has one sibling, Princess Märtha Louise of Norway (born 1971). In 1990, the Norwegian constitution was altered, granting absolute primogeniture to the Norwegian throne, meaning that the eldest child, regardless of gender, takes precedence in the line of succession. This was not, however, done retroactively (as, for example, Sweden had done in 1980), meaning that Haakon continues to take precedence over his older sister.