A linguist and Star Trek fan tried to bring up his son with Klingon as his first language.

Star Trek has developed quite a following from when it came out to now. Fans continue to enjoy the Star Trek series and obsess over it in new ways. For a linguist, the best way to appreciate the Star Trek culture is to learn a little Klingon. 

Klingon (or tlhIngan Hol) is the language of the fictional Klingon species. Klingon was included in the books, but wasn’t used on screen until Star Trek: The Motion Picture. 

Marc Okrand developed Kligon to be used on screen, and would later develop it into a full-fledge language. It has lots of vocabulary for a language mainly used in spacecrafts, but can be difficult to use for everyday sort of things. 

Linguist d'Armond Speers spoke only Klingon to his son Alec, though his mother spoke English to him. Alec rarely responded to his father in Klingon, and by his fifth birthday it was clear he wasn’t interested in speaking it. 

D'Armond Speers switched back to speaking in English with his son. Klingon is believed to have somewhere between 20-30 fluent speakers.

(Source)