Lily became pregnant after a fling with Toby. After a call from her doctor asking her to get tested because of her brother, Lily discovers that Carlton has Down Syndrome. Toby and Lily decide to keep the baby and later find out that he is a boy. This reveals some feelings that the expected parents were keeping from each other. In the Season 4 finale, shortly after Carlton was born, the Kennish and Vasquez family crowds him. John and Kathryn reconcile. Bay asks what the baby's name is and Toby and Lily reveal that his name is Carlton. They chose Carlton because it is the place where they met, (Carlton School for the Deaf).
To be added.