“And behold your eyes see, and the eyes of my brother Benjamin, that it is my mouth that speaks to you. And you will tell my father of all my glory in Egypt, and of all that you have seen, and you will be quick to bring my father down here.”
Now his brothers have recognised that he is indeed Joseph, but it is very difficult to believe. But he refers separately to Benjamin because his previous words had been to those who had betrayed him. So he wants them to let his father know as well, as quickly as possible, and to urge him to come down to Egypt.