One sister was conservator and is now executor, but Probate CT said sibling who refused to help deceased in his care or even allow him into her home, must now share in his estate.
You said that your sister died intestate [no will]. However, you used the word "executor." An executor is someone who is appointed by will. The person who settles an intestate estate is called an "administrator." I'm not sure whether your sister had a will or not.
If she died intestate, then I agree with the prior answer. If she had a will, you would have the right to contest the will. Having the right to do it does not mean that you would be successful. Will contests are often uphill fights. You would have to basically prove that your sister's dementia resulted in her not having the capacity to make a will.
I hope that this helps.
For the purposes of this answer, I will assume that you are correct that the brother who had dementia did not have a will and died intestate (there was some question of this in a previous answer).
The law of intestacy is a fall-back, one-size-fits-all estate plan that the state imposes when a person did not create his own estate plan. The fact that the sister is sharing in the estate presupposes that the brother who died did not have a spouse or children or living parents. That being the case, the law "guesses" that the decedent would want to leave his assets equally to his siblings, no matter what their history. Relying on the intestacy laws for your estate plan, therefore, often creates unjust results.
The fact that he had dementia is really insignificant in any distribution question. Since wills speak only at death, and many people are gravely ill or incompetent prior to their death, it's very often the case that someone is incompetent and in need of assistance prior to his or her death. Only if the will were signed *while* a person is incompetent is the dementia significant.
In either case (will or laws of intestatcy) a beneficiary may act indecently toward a decedent and not be penalized. However if the decedent were competent to make a new will, the beneficiary could be disinherited. Or, if that sibling did something to bring about the death of the decedent, there are avenues to challenge the distribution because of the wrongdoing.
No, you cannot object on those grounds. If the decedent had cared about this, she could have left an estate plan that excluded him. She did not do so, so the court is not going to second guess her. The intestate statute applies rigidly to every situation without a Will and does not permit deviations. This is one of the reasons why every person who CAN do so, should affirmatively PLAN his or her estate, so as not to be forced into an intestate distribution he/she may not have wanted.