"Why does Tommy get a cookie? I want a cookie!" This is a common approach of demand for children. One or other of their siblings or friends got something. Rather than simply asking for the same thing, kids tend to justify their demands by pulling the "fairness" card, i.e. if Tommy gets a cookie, then I should get one too. This phrase of request can lead to numerous problems: a) endless nagging from the "deprived" child until you can't take it anymore; b) instant gratification instead of patience; c) a lack in polite behavior; d) a frustrated parent struggling to explain why Tommy got a cookie and Anita didn't; e) a series of coaxing efforts to stop Anita's ensuing tantrum when told she cannot have a cookie just because Tommy has one.
Before examining each of these detrimental effects, let's look at the potential reasoning behind the child's phraseology in the first place. As children, kids tend to have a purer sense of black and white justice or fairness. If Tommy gets a cookie, so should Anita. When this doesn't happen, Anita feels cheated of what she believes is rightfully hers. Of course, there may be intertwined with the justice a simple want for whatever is at stake, such as the cookie. Most kids seem to think that combining their request/demand with a "Tommy has one" phrase will get them what they want. Such should not be the case.
A. Endless Nagging. When a child hears "No," they tend to question "Why?" oftentimes repeatedly especially if they are rather young. (Of course, if you've taught your children that "no means no," you shouldn't have this particular problem.) Children who question your reasoning tend to do so with whining, complaining and constantly dragging in the "but Tommy has one" in that annoying voice all kids seem to have. Do not give in to their relentless stream of questioning as this will simply lead to more and more frequent questioning. If they doubt your authority in the matter, proceed to the established method of discipline in your family. Just because they ask more than once does not mean the answer will change.
B. Instant vs. Patience. If you simply bow to your child's demands instead of making them wait, they may develop a character of instant gratification. By teaching your children to wait patiently rather than receiving upon demand, you help train their character. This also leads into Point C: Polite Behavior.
C. Polite Behavior. By showing your children how to simply ask for what they want rather than trying to justify it, you teach them a very important lesson. Ask and you shall receive. They don't need to bring into the picture that Tommy has a cookie. They simply need to ask for a cookie. If they do so without complaining or demanding, they will generally receive what they ask for.
D. Frustrated. No parent likes putting up with a whining child. Trying to come up with an explanation for why Tommy has a cookie and Anita does not can be exasperating. The best answer is 3-fold: a) The fact that Tommy has a cookie has nothing to do with whether Anita can have a cookie; b) complaints will not result in receiving the desired object; c) when a parent says no, the answer is no.
E. Coaxing. Some parents will resort to bribing the complaining child with promises of other treats. This is not the correct approach. Rather, life isn't fair. At least not in the moment. Children can have things special from their siblings. Just because Tommy got a cookie does not mean Anita will get one.
Ultimately, try to teach your kids two things. First, that whether or not someone else has the cookie, it will not help them get a cookie themselves. They just need to ask. Second, (and this is in many ways more important), teach your kids to be happy for someone else's good fortune. If Tommy has a cookie, rather than Anita demanding a cookie herself, she could be happy that Tommy has a treat. Good luck instructing your kids with these characteristics. It takes time and effort, but the final effect is worthwhile.