If this is for the Anime, yes and no.
I answered a question slightly different to this at the end of last year, which was asking "How can Legendary Pokémon be shiny if there's only one of them?" Although slightly different the other question is basically asking the same thing you are in your question.
This question can be seen here.
In my answer on the question I linked you to above, I explained that despite many Pokémon fans thinking that Legendary Pokémon are unique (one of a kind), there are in fact only a handful of Legendary Pokémon who are considered to be unique and the only member of their species.