. There are 4 of us that have been named as a successor co-trustees. If 3 of us sign declination to act as successor co trustee do we not get anything

Being a trustee is different from being a beneficiary. Declining to serve as trustee does not take away your right to receive whatever your parents left you in their trust. That said, only sign if you trust your sister who went to the lawyer to administer the trust exactly as it is written, taking absolutely no extra advantage to herself from being in charge. Things to consider: (1) the person (or people) who serve as trustees are entitled to be paid for doing that; (2) it is very cumbersome and slow for four people to serve as trustee. All four of you would have to sign every document. You might talk to your other siblings and see whether the three of you who received letters could agree on only two of you resigning, and the other one staying on as co-trustee with your sister, for some oversight.