Barbara D over at the Scandinavian Royals Message board had a question about the citizenship of the future offspring of Chris O’Neill and Princess Madeleine, as their children will be in line to the Swedish throne.
If the child is born in New York, he or she will automatically receive an American citizenship, as Barbara notes. Or, in fact, because Chris is an American citizen who has recently lived in the Stated, the child will get a US citizenship anyway.
However, in Sweden, the citizenships come through the mother. In both the US and Sweden person can be a citizen of more than one country at the same time. So if the child is born in the US, it will receive a dual Swedish/American citizenship.
One factor is also that Chris O’Neill holds a dual British/American citizenship. According to British citizenship law, British citizenship may descend to one generation born abroad. Thus, the child may end up with a triple citizenship, if the parents so chooses.
But in the end, it would probably be the Swedish diplomatic passport that could solve most issues.