To claim medical expenses, that would be part of your itemized personal deductions. You would only deduct medical expenses in excess of 7.5% of your Adjusted Gross Income. If you're not already itemizing, they may not help you as you can only use itemized deductions if the TOTAL of all of them exceeds your standard deduction. In the case of your mother, her medical expenses would only be deductible by you if she met all the qualifications to be your dependent prior to her death, except that her income could be over $4100.
She's obviously related to you, had to be a US citizen or resident, would not be filing jointly with a spouse, and did not have to live with you.
Lastly, the amounts you distribute to siblings are not deductible by you. If you were the sole beneficiary, the distribution is all taxable to you.
