So how did that happen?
Arsenal have one man to thank for the latest addition to the millions of Gooners around the world, their manager Arsene Wenger.
Speaking yesterday David Beckham said: "Two of them are Man United fans and one of them's an Arsenal fan. I don't know how that happened, but my middle son, Romeo, is an Arsenal fan."
"Actually, I do know how it happened. I took him to an Arsenal game and Arsene Wenger treated him so well, gave him a shirt with his name on the back and his favourite number.
"I had that when I was a kid with Man United. I let them support whoever they want. They don't have to support the teams I played for."
So top marks to Arsene Wenger; if Romeo does go onto become a footballer, he will want like any other to play for his boyhood club and join Arsenal's famous academy. It could be one of the youngest case of player recruitment on record.
Although with Brooklyn and Cruz both Manchester United fans, technically the Red Devils have twice as much chance as the Gunners at prospering from Beckham's dead ball skills being passed on genetically.
Well, they weren't going to support LA Galaxy now were they?
image: © Jeremy Ryan