Photography pose of 3 young children
When you have 3 young children to photograph, a chair can be used to support the baby.
I had the oldest and tallest child kneel down on the right. The middle child stood behind the chair and the baby was safely secure in the wicker chair.
When portrait poses include young babies, it is important to pose everyone in the photograph so their heads are fairly close to each other.
This allows you to compose in close so that the baby is not too small in the portrait.
Photography poses of children are very dependent on the size of the children and each situation may be different.
Baby Portrait Books at Amazon.
A good permanent source of ideas for poses can be had by buying a portrait photography book that concentrates on the posing of children.