When we got rid of all our Duplo sets arguments between two siblings stopped. But they soon commence again when it comes to having the few toys we had left; the arguments that began to break out again were mainly about sharing and what belongs to who.
There is a small 3 and a half age gap between the two so the youngest who is 2, doesn’t really understand yet whereas the older one is very aware just stubborn!
Our solution was to buy dressing up outfits; one each – so they could play together, exactly the same. This way, the eldest uses her imagination and the youngest, who doesn’t have clue what’s going on really, follows the eldest around; feeling like she’s involved in the game.