Can brother with Power of Attorney sell my mothers land even though her estate equally disposed to us both?

Incapacited mother (94 in Care) does not agree with any of the brothers legal and financial decisions and he is not interested except to use all her money to employ his solicitor to oppose both mothers and my objections...very successfully despite Guardianship office maladministration. Employs all his relatives and friends to denigrate his brothers life , behaviour and motivation on behalf of his mother.They ,in turn write to Court en masse to submit false or hearsay evidence from him and his family.
It would seem in character for him to sell her land and continue to use her money to legally alienate his brother out of jealousy and greed.
What can be done ?

If the power of attorney was given by mother at a time when she was legally competent to do so, and if the power of attorney includes the right to dispose of property, and if mother is still alive, then the brother holding the power of attorney can dispose of mother's property.

A power of attorney is extinguished on mother's death, at which time her will should dispose of any property still remaining in her estate.

EDIT - she can revoke the power of attorney unless by "incapacitated" you mean that she is no longer legally competent to do so.

YES he can sell the land as power of attorne. The ONLY thing that you could do to prevent that is to have her revoke it.

Brother is taking advantage of his authority, contact attorney and have him removed as power of attorney.

Get an attorney and have your mom change the POA so the brother no longer has power - or discuss with an attorney what can be done in this situation.

She can always cancel the POA.

Then she better cancel that POA or the person with it can do as he pleases.

Yes.