Hi ... don't worry. it's very common in every home. My 2 kids are with little age difference and they quarrel for every little thing. Now both of my kids have reached to a stage, they are equally developing in almost everything. Try to engage both of them in a game where they love to play without any time constraints. Teach both of your kids that they are siblings to each other who need to shower love and affection on one another forever. Till they understand you need to be with them and Try teaching them that they need to play without quarreling with the available toys in fact explain to them that both have the same set of toys. once you start observing any change, Appreciate their coordination whenever you find them they are playing with mutual understanding. Participate in the game along with them and try teaching them how they can enjoy playing together. for example, if both like to play with toy airplanes then tell them that you both are pilots one will take off the flight and the other one will land. children will always like trying different. Take them to a nearby park and buy a small ring or a ball where you can teach them to play with a single ball. Try making them mingle with nearby kids to play accordingly. Last but not least. don't lose patience. Kids tend to behave so teaching them multiple times will definitely make them understand what are you trying to teach. Also never yell or scare them while teaching positive things. Little appreciation gifts are fine once in a while when they learn new things. But don't make it a habit. Love and patience is the only key to raise them with discipline.