rights in Father in law property for grandchildern

Hi My father in law died in Fabruary 2018. my mother in law lives alone . we have managed a servent there, I live in germany since 7 years. We conducted all the right at his demise with our own money. My sister in law lives in same city and now she is misguiding my mother in law to sell the house and shift with her. She influences my husband also. I dont want to sell the house. Do i or my son or daughter have any right over the property. can we claim a part. how can i stop this process legally