my mom expired now one sibling wants to start a lawsuit, but the other family don't want to pursuit with it what do we do/

All siblings do no have to agree to bring a lawsuit on behalf of their mother. It only take one sibling to proceed. That sibling would have to be appointed personal representative for the specific purpose of bring the lawsuit. This is a complicated issue and I would hightly recommend speaking to an attorney.   This response is general in nature and is not legal advice. No attorney client relationship is formed by it. Further, the response does not represent the opinions or views of LexisNexis or its affiliated companies.