Deceased parent

I am the eldest of 4. I was a joint owner on moms bank accounts. Her wishes were to divide equally the cash between the 4 of us. She stated in her Will that her estate and a inherited Ira be equally split 4 ways. That’s all she had. The Ira stated the 4 of us as equal beneficiaries.

I have split the bank accounts 4 ways but I was told I have to file taxes showing the “gift” made by moms request. Remember they were joint cash accounts at the bank.