The success of "Descendants of the Sun" has given star Song Joong-ki's career a big boost. But with the success also comes problems as the actor's privacy has been compromised.

The Korean actor is currently on a press tour in China, meeting and greeting his international fans. The trip appears to be a massive success, as the "Running Man" star has reportedly charmed millions of fans with his good looks and wit. His answer to a question about his sister also captivated fans who were surprised at how protective he is of his sibling.

During a fan meeting in Guangzhou, China, the 30-year-old was asked by a fan what he would do if his younger sister liked his best friend, Lee Kwang-soo. He immediately shut down the idea and said that while Kwang-soo is one of his best friends, he won't allow it because he's too tall. Aside from the height, Joong-ki added that his friend and his sister are not a good match because Kwang-soo is so much older.

The star of "Sungkyunkwan Scandal" is protective of his friend as well. When asked by another fan which friend he would save if both were drowning — Park Bo Gum or Lee Kwang-soo — the actor replied that he would actually prevent the two from going near the water in the first place.

The popularity of "Descendants of the Sun" has also made Joong-ki one of the most popular endorsers in South Korea. The actor has been South Korea's top CF model for the past three months, carrying brands like Top Ten, Jeju Air, Domino's Pizza, and Baskin-Robbins.

Unfortunately, that popularity also leads to an invasion of privacy, like the recent leak of his passport photo. It appears that a photo of the actor's passport was taken without his knowledge and was later released online. The culprit in this privacy breach is still unknown, but many suspect that it was a customs officer.