The Duke of Cambridge was in Cardiff hosting a reception for injured rugby players and their families when he made the sweet comments about his family life.
Talking about Princess Charlotte, Prince William said: '[She is] very sweet, but all fathers say "just you wait, when you get to nine, 10, 11 they go crazy." I'm looking forward to it, there will be some drama.'
William also joked that Prince George, who started nursery this year, and Charlotte are already a handful.
'No broken bones yet, but they're trying,' he said. '[They're] running around, pushing things, jumping. Please tell me it gets easier.'
The second in line to the throne flew to Wales for the reception from Norfolk, after working shifts as an ambulance pilot from Monday to Thursday.
He told the BBC: 'I love my rugby. Having lived in Wales for four years, worked here and seen the rugby I'm thrilled to be back. When the Welsh anthem goes, you know you are in Cardiff.'
Despite dividing his time between his job, royal engagements and his family, Prince William was recently accused of being 'lazy', and criticised for only having attended two royal engagements this year.
He will soon be heading to India and Bhutan with wife Kate in April for a six-day visit, while Prince Harry will be visiting Nepal in March.
Before William's lovely comments about his children, George and Charlotte's mum had also recently talked about them in the blog post she wrote for the Huffington Post during her stint as a guest editor, where she revealed they're encouraged to talk about their feelings.
'Like most parents today, William and I would not hesitate to seek help for our children if they needed it', she wrote.
'We hope to encourage George and Charlotte to speak about their feelings, and to give them the tools and sensitivity to be supportive peers to their friends as they get older. We know there is no shame in a young child struggling with their emotions or suffering from a mental illness.'