For us, it's winter right now, which means a lot more time inside together. There are definite benefits to this, like cozying up together more, slowing down, reading books, and all of that, but it can also be a time of rising tensions and tempers. It's hard when kids are cooped up (for some, this happens a lot in the summer, too) because personalities that may clash here and there are now forced to be together more. Here are a few ways we've found to combat sibling fights:
Give kids who are fighting a lot more jobs together. It may seem counterintuitive to have them spend more time together, but these sibling relationships are excellent practice for the future. Sometimes you just need to work with that person who's annoying you and learn to get through it. I've seen kids who work jobs together get closer after these tasks, too, because they now have this thing that they did together in common.
Sometimes it's just a season where kids (often ones very close in age) are just getting on each other's nerves, so we will separate those kids for a while in the vehicles, specifically. Moving the car seats away from each other for a bit may be the best answer for everyone, at least for now.
We also don't encourage tattletales, unless someone is going to get hurt. It's really important for the kids to learn to work out these small disagreements they're having without telling on their siblings all the time. Again, this is good long term for them having confrontations with others and having to figure out how to work it out themselves.
So, our techniques for sibling fights range from forcing them more together to separating them, depending on the season and the kids. I hope some of this can help you!