Who needs a sibling to stick out a tongue to, to make funny faces at, to fight for the same toy, to have a "see who can outscream" challenge, to boss and be bossed about by, or simply to get on each others nerves. I found that someone need not be a sibling. Cousins do the job just fine. At least we have not reached the stage of crucifying with a pencil lead into the palm of another. Mii believes that the 2B lead was what made Aunt El smarter than her.