My sister sold my mothers house 2014! She was power of attorney and kept the money! The will said split it with my brother and I! Is this legal

If your sister sold the house and gave the money to herself, she might be in violation of the terms of the power of attorney.  Unless the power of atotrney specifically allows for gifting, the agent operating under the POA cannot gift money to themselves.  You need to look at the POA document and see if it allows gifting.  If your sister sold the house using the POA then the POA is filed along with the deed and can be found online.