While attending a rugby match in Wales on Friday, the prince, 33, quipped about how his kids were getting up to mischief at home.
"No broken bones yet, but they're trying. Running around, pushing things, jumping. Please tell me it gets easier," he said when asked about his lively children, 2-year-old Prince George and 9-month-old Princess Charlotte.
Before the game, William met with injured rugby players and their families at a reception hosted by the Welsh Rugby Charitable Trust at the Principality Stadium in Cardiff, where he revealed a few fun details about his little ones.
"Charlotte is very easy, very sweet, but all the fathers say, 'Just you wait, when you get to 9, 10, 11, they go crazy,' " he said, adding, "I'm looking forward to it, there will be some drama."
William also chatted with Frances Bateman, 34, a rugby player who suffered a brain injury while playing for Gwernyfed Ladies.
William realized they had met before when she reminded him she had shown him a charity calendar of naked female rugby players during a visit to the stadium in 2014.
"I got into a lot of trouble over that,” he laughed.
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Steve Coles, 44, asked William about his rugby rivalry with his brother Prince Harry, who supports England’s team.
Steve, who was left a paraplegic after an accident he had while playing for Abergavenny, asked the prince, "Did you stick it up Harry after the World Cup?" (Wales beat England.)
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The competitive prince laughed and said, "Yes, don't worry, we had some interesting conversations."
William flew by helicopter to the match in Cardiff. And he shared a little about his job as an air ambulance pilot, saying, "It's good, it's different. The medical side, I get involved in it, it's fascinating."