The Real Madrid player, 29, kept his arms around a smartly dressed little Cristiano Jr. as they watched the action on Thursday (8 May).
Cristiano announced the birth of his only child in July 2010. The mother has always remained anonymous with Cristiano having 'exclusive custody' of the youngster.
Yesterday, he played the doting dad courtside as he ensured Cristiano Jr. was shielded from the blazing son with an oversized hat and sunglasses.
Cristiano spoke in 2012 about how much he loved being a father, telling CNN: "I think it's the best thing in life to have a kid. It's like a dream. To wake up in the morning and to see him and him say, 'Daddy, Daddy'. It's great. I love it."
The footballer's Russian supermodel girlfriend Irina Shayk wasn't at today's tennis match although she is frequently seen in Madrid with the star and his son.
In January, she joined them in Zurich to see Cristiano named FIFA World Player of the Year for the second time. An emotional Cristiano walked the red carpet with Irina and his son, before his son joined him on stage to accept the award.
Irina has been in Washington DC this week, where she attended the star-studded White House Correspondents' Association Dinner.
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