William, Prince of Wales, is next in line to the British throne, followed by his children.
William has mostly continued with royal engagements during Kate's absence. An exception was the memorial service for his godfather, King Constantine, which he pulled out of last minute on February 27.
"HRH will continue to balance supporting his wife and family and maintaining his official duties as he has done since the start of the year," a Kensington Palace spokesperson told Business Insider, using the abbreviation for "his royal highness."
Royal biographer Phil Dampier previously told BI that the monarchy "could, with the wrong unforeseen circumstances, collapse quite quickly," if something were to happen to both the king and William.
"It could lose a lot of power and ability to operate if god forbid, some other disaster happened," he said.