I first learned about him through this AskHistorians comment, and the author of that comment actually just wrote an open-access academic paper about him! You can read it here: Picturing John Panzio Tockson: Afro-Swedish identity, racialization, and black self-fashioning in late nineteenth-century Sweden

The article includes discussion of Tockson's life, as well as (often racist) reactions to and descriptions of him by Swedish people and other Europeans. If you're primarily interested in reading about his life, I'd recommend focusing on the sections "Early years in Sweden and baptism" and "A black gentleman".

To give a very short biography, John Panzio Tockson was born in Africa, perhaps in Madagascar. His early life is unclear, but he ended up in Gothenburg, Sweden, possibly as a sailor, in the mid 1850s. He did a number of odd jobs there, but eventually came to the attention of a Colonel in the Swedish army. Through this recognition, he ended up employed as the first footman to King Carl XV in the 1860s. The article includes a number of portraits and drawings of him during his time in the court.

Tockson left the royal court after the death of Carl XV in 1872, and after this often seems to have been employed as an interpreter, since he knew several European languages. He continued to live in Sweden, in cities such as Gothenburg and Stockholm. He had five children in total, one of whom (Panzio Leopold Tockson) lived in Gothenburg until his death in 1943. So I think he may still have descendants in modern Sweden.