They had a lot of time on their journey home to work out what to say to their father.
They certainly didn’t blurt anything out on the spur of the moment. They feared that if they did, the shock would be too much for the old man and might even kill him. So they spoke to him in two stages: first, “Joseph is alive!” and second, “he is a ruler in Egypt!”
What does Jacob respond? “It’s enough!”
What is enough? What was important to Jacob was not Joseph’s greatness and status in Egypt, but the fact that he was alive after all those years of doubt and apprehension. Hence Jacob says to his sons, “It is enough (to know that) Joseph is still alive!” (Gen. 45:28).