Replying to @irina@wandering.shop
@irina @sjaakkeuvelaar @hengstenberg @rauschma
To date, one reported case of a child being brought up to be a native speaker of Klingon. Failed, partly because insufficient pool of others to talk to, partly because the language is not yet developed enough to be used for daily tasks, and partly because the child (Alec Speers) simply refused to continue using the language once he reached about 5 years old.
By comparison there are a few thousand native speakers of Esperanto.