If you're bigger and stronger, it's time to start playing the same dirty tricks games that your siblings are playing.
If one of them hits you, you hit them back twice as hard and twice as much and you go straight to your parents and complain about them hitting you and make out that you didn't hit them.
Normally I am against violence and lying, but this is a case of self defence. And in that situation you've gotta do what you've gotta do to preserve your health and safety.
If they steal your stuff, you should give them a warning, if they don't return your stuff and stop stealing from you, you punish them.
This is again self defence. As everyone has the right to be master of their own property.
Please be pragmatic on this. There may be presents that were given to you, but it's no big deal if anyone in the family takes it and uses it. In that case, mentally release control of the item. Consider it a family possession.
When you are given unfair punishments by your parents, try to weasel your way out of them.
Sometimes it will be worth you getting into trouble with your parents, as long as you have given a big enough deterrent to your siblings to not hit you and not steal your stuff.
Up till now your siblings have been "trained" - in the broadest sense of the word - to hit you and steal your stuff.
It's time for you to retrain them. Even if the training comes at some cost to you.
Look to move out as soon as you reasonably can. So that you get out of this nightmare of this poorly managed home.
Try to do good stuff with your siblings. Such as playing football / cricket / rounders in the park with them and a few friends. Something that will burn up their energy. And where you take the lead in organising and supervising the activity.