Cristiano Ronaldo, the Real Madrid forward and Portugal captain, has used his imagination productively by naming his son Cristiano Ronaldo, his sister, Katia, has revealed."The baby is doing very well, his sister said. "We are looking after him while Cristiano is away. He's called Cristiano just like his dad. Cristiano chose the name but we like it. He looks like his father and like me. He has the same eyes. We don't know the mother, we never met her."

Ronaldo, who is believed to be on holiday in the United States with his girlfriend Irina Shayk, announced last week that he had become a father on his Twitter feed and Facebook wall but has refused to reveal the identity of the child's mother.

This secrecy has led to speculation in the Portuguese press that the baby is the product of a surrogacy arrangement. "Some people may think it's strange, but we don't. We're very happy about what Cristiano has done," said Katia.

Ronaldo's mother Dolores, 55, confirmed her grandson had been born in the US, but the family refused to elaborate on the rumours about the details of the boy's parentage.