And asked whether he could give the new baby any advice or "strategy" on being a younger sibling, he said: "There's never a strategy. I think George will be over the moon. I think he will be thrilled having another small younger brother or sister."
After welcoming teams from 13 nations competing in the games, Harry travelled to the Barking Sporthouse and Gym at Mayesbrook Park, Dagenham, to meet other competitors.
Meanwhile, The Duke of Cambridge today said he and his wife were "thrilled" to be having a second child - but admitted Kate has had a "tricky week or so" after falling ill with severe morning sickness.
Watch: Prince William: 'Thrilled' by second baby
Prince William was forced to attend an engagement in Oxford alone today because the Duchess was too unwell to come with him.
He said: "She's feeling okay. It's been a tricky few days - week or so - but obviously we're basically thrilled, it's great news, and early days. We're hoping things settle down and she feels a bit better."
Kensington Palace announced today that the Duchess was pregnant again. Kate, 32, whose son, Prince George is just a year old, is expecting her second baby with William next year.
The Duchess is again suffering from the debilitating condition hyperemesis gravidarum, which causes extreme sickness in pregnant women - but William said she may be over the worst of it in a fortnight.
Unlike her first pregnancy, however, Kate is being treated by doctors at Kensington Palace and has not been admitted to hospital.
- Daily Mail
