Painter of portraits and landscapes, Charles Mertens was a student of Verlat at the Fine Arts in Antwerp, Mertens' home town. He participated in the creation of the XIII group. The circle of XIII was founded in February 1891. The circle of XIII is formed by dissidents of the Antwerp group Als ik Kan. The circle consisted notably Léon Abry, Emile Claus (who still lived Antwerp), Edouard de Jans, Henri De Smeth, Edgard Farasyn Maurice Hagemans, Frans Hens, Evert Larock, Romain Looymans, Charles Mertens, Henry Luyten, Henry Rul, Leo van Aken, Louis Van Engelen, Piet Verhaert and Théodore Verstraete.

The circle lasted until 1899, and only organized three exhibitions during its existence. Notable artists were also invited to these shows...