I think every family, with more than one off-spring, has it--you know, the look. It's hard to describe as every family has its own version. I know my family has it. The look ranges in various degrees. The mildest is like a warning and the strongest is a "time out."
I grew up as the middle child--with a Big Brother and a Little Sister. Being in the middle is no fun. You're either ranked as "too young" for the privileges of later curfews and later bedtimes like Big Brother or "old enough to know better" for not stopping Little Sister from misbehaving. And in the midst of this confusing age thing, earning the parental look.
Reflecting back, I think we all got the look at various times during our childhood. During our ruckus and noisy sibling squabbles, one or the other parent would look into our room, quietly say our names and give the look. It always worked--like a switch had suddenly turned down the noise. Note, I said "turned down the noise" and not "turned off."
The look worked especially well in a room full of company. At family dinners, if the pushing/shoving/giggling became too much at the table, one of the parents would look over and give the secret family you-know-what. I noticed that my aunts and uncles also did this with my cousins. We woulds all stop except for the feet kicking under the table.
I was thinking about this when my cousin looked over at his two children, noisily wrestling over the mini-racing cars in the toy box. He gave his sons this look without uttering a word. My sister has this natural teaching skills and so the look was easy for her. It must be passed along in the DNA because the kids learn the meaning of a parental look before they can talk.
I never knew I had this ability to give the look until my little granddaughter looked up from bashing her wooden blocks on the kitchen floor. For three nano-seconds, she stopped her happy squealing, threw me a big smile and a "luff you Po-Po" before resuming her noisy activity. I think I need to practice this look some more, but not right now. . .