Right, despite the fact that my DS1 was so pissed off when his little brother was born (he was 2.5), that he once said "Mummy, can you go out of the room so I can hit Charlie",
and despite the fact that for the first few years they took turns to wake up every night,
and despite the fact that when one was going into tantrum age the other was just coming out, so it was basically 4 years of tantrums,
and despite the fact that we used to go out sometimes with BOTH of them having bite-marks on their faces......
DS2 smiled his first smile at DS1, and said his first word to him as well. When they start to communicate with each other it is brilliant.
My 2 boys are now (despite the bickering) the best of mates, will walk down the street holding hands and laugh like drains at each others jokes, and have learned so much from each other about getting along with someone very different from themselves. They are 6 and 8.
It is very hard but it will gradually get better !