My siblings withdrew Mom's IRA account and she became upset. What can I do?

Look, if you verify this occurred the way you said it did- fraudulently - then embarrassing or no, you go to the legal authorities, and go immediately. That IRA is for your mother's needs, not your siblings' addictions or other "needs", and the "gifting" of such an amount will be a disaster if she needs Medicaid. If the siblings have POA, they have abused it and could probably be removed unless there is a reason the money had to be taken and used in some way on Mom's behalf.

The bank isn't going to tell you anything, unless you are on the accounts or are POA. Who is financial POA?

If this was theft, you go to the District Attorney's office. If the siblings are on the account, then, your mom may be out of luck.

My mother recently thought that my sister had written a check for $12,000. It wasn't so. My mother had signed the check herself, to the NH.

Good idea! Mom can contact bank and get the info..

Instead of questioning your sister I would check with the bank manager to see how this transaction was completed.

No they never asked her, she did not even know about it, until that day, she had told my sister she wanted to see her bank statement, but my sister would never bring it. my mother is 85, she' your topically aged mother, but she is competent, I will ask her if they had her to sign anything, but I know she did not, she"s in the nursing home because she had replacement hip surgery, sometimes shes a little
off, especially when they give her to much medication, but the doctor told her she could come home as long as she has some help sometimes. she can get up and down, bath herself, dress herself.

How did your brother and sister manage to withdraw funds from your mother's IRA account? You cannot just walk into a bank and withdraw that large sum of money without identification and a paper trail. If your mother's signature was forged that is grand larceny. Even if one of them has DPOA, they need your mother's permission to withdraw any sums of money if she is still considered competent.

were do I go to do this, it's embarrassing that my own brother and sister did this, they haven't even spoke to me and my other sister for 3 months, they never have to discuss any changes they make for mom, actually my other sister has a drinking problem, they have treated her like dirt her whole life, mad cause I take up for her, someone has too.and that"s the whole problem in a nut shell.

File charges for financial abuse and exploitation of a senior.