He owns a vineyard. It has been in his family for 3 generations. But the vineyard had been already existed before being bought by his family. Just take out, "had been already," as below: But the vineyard existed before being bought by his family. That's it -- well done! :-)

Hi! If you want corrections, you should submit this as a notebook entry. This space is for asking specific questions. That said, you did well, except that you need to say "It had already existed..." No need for "been." You could also say it had already been in existence.