You asked

My two kids are always competing with each other. Should I be worried?

A little competition never did anyone any harm but little ones should not be so focused on winning that they miss out on the fun.Your children can learn invaluable lessons from winning and losing and you will notice that their skills will improve the more they push themselves. However, it is important that you don’t allow their competitive streak get out of hand.
Teach your youngsters to be a good winner and a good loser and to always play by the rules. A good winner knows not to brag and a good loser knows not to sulk. It is important to instil this at a young age because while it may be ok for a little kid to throw a strop if they lose it is not ok for say a teenager.
Playing by the rules is also important as it means the game is fair to all. If your child finds it hard to understand the rules of the game, either suggest they try something a little easier or simplify it for them.
It is vital that you teach them that winning is not the most important part but rather the taking part. This way they will be able to enjoy the game without the pressure of having to win.
Unfortunately, a normally calm game can get out of control fairly quickly if the players are both overly competitive. If rules keep changing or one kid starts to cheat, it is time to wrap the game up. When kids are overly competitive they may start to evaluate themselves on their victories and may avoid getting involved in another game until they win the first.
If this sounds familiar, talk to your little one to find out what the problem is. It could be that the younger sibling is simply looking up to the older sibling and wants to be like them. Ensure they put things in perspective and never put pressure on them to win.
However, if one sibling always wins against the other, sit down with them and suggest they give their brother or sister a headstart or handicap. This way everyone gets a chance to win, even if one is more skilled than the other. 

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