The present invention generally relates to passenger aircraft seats. Some examples provide systems for integrating a child seat into a certified aircraft seat. Some examples include a passenger seat backrest having an integrated child seat. An integrated child seat base may be moved between a stowed position and a deployed position. When in the stowed position, the integrated child seat base may fit within a recessed surface of the seat backrest and the seat may then accommodate an adult passenger. When in a deployed position, the integrated child seat may then accommodate a child passenger. The integrated seat may include a harness system that extends through the seat backrest and couples with an internal support structure of seat backrest. In some embodiments the mounting points of the harness system may be reinforced with stiff brackets attached to the internal support structure.