I have 2 kids that are 4 years apart.
All along, I have explained to my eldest, about how her younger brother is developing, in terms of understanding things or not, as compared to her.
And this has helped, my eldest in understanding... what her younger brother may be thinking or doing and why. Thus, it helps in any fights they may have and the expectations my eldest has of her younger brother.
For real disputes, I step in. And appropriately discipline them.
I also, taught them and tell them that they each can have alone time. IF one of them simply does not want to play with the other, they CAN say so. And it should be respected. Siblings are not always in the mood, to always be playing with each other. It can be irritating etc.
My kids are very close, but at times they simply get on the others nerves. So, I taught them that they need to speak up and say so... nicely, then its fine. And they do this. And then SAY that they want to just play by themselves etc. Its fine. I don't expect my kids to be joined at the hip.
I also do not tell them, that telling me something is "tattling." I teach them that they can tell me anything... about what bothers them or what the other did to them when it is beyond their patience. If something is important to them or they are frustrated, to tell me. It is not, tattling.
There were many times when my eldest daughter may be irking my younger son. And my son would tell her to stop it, in a nice way. And he would be REPEATEDLY telling her this, but she didn't stop. THEN my son would get mad and then they'd be yelling at each other. SO... I explained to my daughter, that her brother was TRYING to tell her to stop, nicely, and for several times already. He TRIED, but she didn't listen. And now... he is at the END of his patience and is now, angry. SO SHE NEEDS TO, be aware of his cues. He already SAID to stop, but she didn't. So she needs to, ALSO curb her ignoring a person's warning. It takes, two. And she was wrong.