Who is the mother of Song Joong-ki's child?

Song Joong-ki does not have any children yet. He is married to actress Song Hye-kyo and they have not announced any plans of having kids.

Song Joong-ki was previously in a relationship with actress Park Bo-young, but the couple split up in 2011. They did not have any children together.

So, currently, the mother of Song Joong-ki's child is not known as he has yet to have any children.