First of all remove this fear from your mind. Just dont be scared.It good to hear that you are serious about JEE and if you can convert this seriousness into real efforts and outcomes definitely you will be in IIT like your brother.
You have to get your basics very very clear.
Right now you can refer the following books and rest you will come to know when you go to Kota...
Maths: ML khanna, RD sharma , Arihant publications
Physics: HC verma, IS irodov
Chemistry: P bahadur, Soloman, JD LEE
We are all IITians and here to help you in your IIT JEE preparation.
All the best.
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