Castro uses his mother's last name because the man who had a relationship with Veronica Castro by the time she became pregnant with Cristian, Loco Valdes, always had an icy relationship with his son. As a matter of a fact, Valdes did not attend his son's 2003 wedding with a Paraguayan girl. Another reason that he chooses to use his mother's last name is that he lists her as his number one idol in life.
After participating in various telenovelas and recording some albums as a teenager, Castro began his internacionalization in 1993, starting with concerts in Puerto Rico. As a matter of a fact, he dedicated a song to that country in his second album, as a way to thank the Puerto Rican public's backing of his career. Castro became an international teen idol and sex symbol almost instantly after he began touring, and he began what has been a fructiferous international singing career.
During the late 1990s, he dated an Argentine girl for some time. The couple was involved in a small scandal one time, when they arrived at Miami International Airport, to be hounded by a reporter who also had trouble with Alejandro Fernandez and Luis Miguel, among others. The reporter asked Cristian's girlfriend a personal question, and Cristian reacted by slapping him across the face. The incident, which was filmed on camera, was shown on tabloid television shows several times.
After breaking up with his Argentine girlfriend, Castro met a Paraguayan girl, daughter of a rich man. They got married in Asuncion.
Apart from the reporter slapping scandal, Castro is known for his accessibility to fans, and its not uncommon to see papparatzi photos showing him stopping to sign an autograph for a fan or taking pictures with them.