Did King Louis have a son that disappeared?

Do you mean Louis XVI, who was guillotined in 1793? His son is believed to have died in 1795, although there are always other wild ideas afloat. But that's why the next king called himself Louis XVIII, leaving a number vacant for the poor kid, who was only ten years old in 1795. The name of the boy was Louis Charles de Bourbon, and became Louis XVII on the death of his father on January 21st 1793, as the French guillotined the King of France Louis XVI. He was held prisoner and was abused and tortured in a horrible way by his keepers. His mother was Marie Antoinette. The French also guilotined her in 1793, but before they did so, they took him away from her, imprisoned him in a dark cell and forced him to drink alcohol and sing revolutionary songs. They even made him sign a document saying he was sexually abused by his mother and aunt, which was absolutely not true, but the French needed an excuse to let all the rest of the country see her as an animal instead of a poor inocent woman. Louis Charles died in 1795 in his prison. His heart was taken out (this was the normal custom with French princes) and is still on display today in the St Denis cathedral in Paris. Some say he had escaped prison and was switched with a different boy, but this is not true. The rest of his body was never recovered, but with DNA testing on the heart and Marie Antouinette's hair, it was 99,9% proven that it was his heart.