Phillip continued to learn how to smile and laugh - by the end of December he was 4 months old, and could lift his head up consistently while on his belly and look around, and even try to grab things. He liked to make sounds with mommy and daddy, especially a raspy ggggggrrrr sound coming from the back of his throat. He also learned how to roll over from his tummy onto his back (which has been shown in this previous post).
Here a short video of him laughing, followed by some pictures.
Even from the very beginning, Cecilia was so good with Phillip.
This was when Phillip was 4 months old, but even now, if he starts crying, Cecilia will go to him and try and make him laugh, or feed him something. She is such a good big sister.