It is important to make sure all children are properly acclimated to their new siblings when blending a family.  Of course by blending I mean natural children and their furry predecessors.   Brett and I achieve this by breaking in our cats to their new, more dominant sisters much as one would do when training a horse to be ridden.  The picture below illustrates.  As you can see, Corky is now submissive to Clare and has accepted her into the family hierarchy.