A silhouette is a creative way to capture a portrait. To get a silhouette effect, have your partner and little one stand in front of a window/door.
Your camera’s exposure is automatically going to try and balance between the bright background and the dark subject, so in order to get the silhouette effect, tap and hold down on the screen to lock the exposure and then drag your finger down so it gets darker. This will give you a silhouette effect. See how in this video: