Usually, the person who owns the property writes the will (or has their lawyer do it) about how the property is disposed. It may be different in India, but in the US,
What about revising the will and making it "equal" but not necessarily that you and your brother divide everything in half?Maybe you get all of the jewelry but brother gets more of something else, and his wife gets something that she might actually want or like. Many times an estate is not divided exactly equally but the survivors do get things that have value to them. Any cash value should be divided equally between you and your brother unless your mother stipulates differently.
Will a will handwritten by a beneficiary be accepted as legal in India? Even if your brother does not contest it? You might want to look into that and/or get your mom to an attorney anyway, as others have suggested, to make sure that problems related to the will do not come up when she dies.
I can only speak from my own experiences.