The Prince is currently training for his Bond Air Services job with the East Anglian Air Ambulance, which is currently based in three locations: Cambridge, Norwich, and Staverton. It is possible he will be working when his wife goes into labor, but a source tells Us Weekly he will "never be more than a couple hours drive from London."
William's brother, Prince Harry, could also potentially be away during the birth for military reasons.
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Us reports that the royal baby's sibling-to-be Prince George could also be absent at the delivery, but that decision will be made when Kate goes into labor.
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As royal officials are heavy in prep mode, one other thing they don't know, like the rest of the world, is the gender of the baby.
"Like last time, the Duke and Duchess do not know if the baby will be a boy or a girl," the source told Us.