Choose any letters you want, but the parents must have the same initials and the children must all have the same initials. (The parents and children do not have to have the same.)
SO1:
SO2:
(Feel free to add additional parents.)
DS/DS:
DD:
DS:
DD:
DD:
DS/DD/DD:
DS:
DS:
DD:
Pet: (Doesn't have to have a middle, but the first name should start with the same letter as either the parents or children.)