We were lucky with him and never really had the "Terrible Twos". We thought we were in the clear, but realized with him, it was more like the "Terrible Threes". Then four hit...we had no idea what we were in for. Welcome to the "Fierce Fours".
Oh the look!! Watch out Mama. I noticed that with my oldest son too, something changed in him when he started to compete with his little sister. Good luck with it!