we're going to be three instead of two

The newlywed wife said to her husband when he returned from work, "I have great news for you. Pretty soon, we're going to be three in this house instead of two." Her husband ran to her with a smile on his face and delight in his eyes. He was glowing of happiness when she said, "I'm glad that you feel this way since tomorrow morning, my mother moves in with us." (from Irina Nisanova)