The newborn boy is 10/1 to play in the Premier League like his father, but with far longer odds to turn out for either of his teams.
Klay is rated 50/1 with Ladbrokes to appear for Manchester United, 100/1 to play for Everton and the same odds to earn a senior England cap.
The bookmaker also offers odds on the Rooneys continuing the trend of baby names beginning with K, having also named their first son Kai.
Punters can get 5/4 on the third Rooney child following suit, or 4/6 on Wayne and Coleen opting for a name beginning with a different letter upon having another baby.
Any member of the Rooney family advertising Special K cereal is rated at 20/1, while the following names are all given long odds:
- Kourtney 25/1
- Karter 33/1
- Kassius 40/1
- Kris 40/1
- Khloe 50/1
- Kim 50/1
- Krystal 66/1
- Kristy 66/1
- Kanye 80/1
- Keith 100/1
- Kevin 100/1
- Kallum 100/1
More top news
Jimmy Sinclair, who has waited his whole life to vote for independence, told us he was "disappointed" after the 'No' vote.
Photos from an historic day in Scotland's history as voters choose to remain part of the United Kingdom.
Is Manchester really more powerful than Wales and Northern Ireland? Find out how the union's four nations compare with England's regions.