How to get money back from siblings?

My mom lives on about $29,000 per year, in her own home. She "makes" too much money to qualify for any government help. She currently has me coming in 3-5x per week, and another lady 1-2x per week, but both of us think she needs more care, and neither of us can give any more time. And mom can't really afford to pay for another caregiver.

However, about 5-10 years ago, she had "parked" some money with 3 of 5 kids, with the understanding that if she needed it in the future, they would pay it back to her. (I know, this was a REALLY BAD IDEA, but it wasn't me who suggested it to her, it was her former poa, who was one of the recipients of money).

The reason only 3 of 5 got money, was the other 2 had legal troubles going on with divorce and child custody battles. So they got nothing, because it would have complicated Their Issues.

As my mom's poa, she asks me all the time, to get those monies back from me and the 2 siblings that also got funds.

I feel like I want to give her back some of the money, because I can see on a daily basis, how much she needs it...and I have told my mom that I would like to give her the money back, but, the other 2 sibs should give back an equal amount, at the same time. I've told her that she herself should do the asking since she was the one who did the giving. And I've also told her it was a Really Bad idea to have done it, because there was no contract or paperwork.

So, if I were to give back everything mom gave me, but the other 2 didn't, then when mom dies, how do I account for that? (I am the executor, so if I tried to deduct the money from their share of estate, they might file a claim saying I didn't divide everything equally).

And if mom were to need Medical Assistance (after using up all her money) then how would that be handled? My money would be gone, but the other kids who got some, would still have theirs, but myself and 2 siblings would have nothing at all from the estate (assuming she uses up all her savings).

I cannot ask mom's attorney about this, because he is very expensive, and this issue is so complicated--I'm sure it would take more than a 10 minute phone call. It would probably cost several thousand dollars.

So, is this money given away with a mostly verbal agreement, simply gone?

And if it is "gone" then is it totally gone, when I settle her estate? because the other 2 kids didnt' get anything, so my mom always says I have to adjust the estate shares. And the 2 who didn't get any, definitely know that they didn't get any (and they are expecting an adjustment in their share of any inheritance).

Her Will document makes no mention of these gift monies, at all.

Mom is still very much competent, and able to re-write her will, so maybe I need to take her to that expensive attorney and have her will re-written to address these gift monies???

Or would the other 2 siblings contest the will, claiming they never got any gift monies? I have no documentation that they received it, other than mom's word.

The amounts of money given were between $8-13,000, always under the gift giving limit of the IRS.