2. The estimate of 20 square meters of rural houses is rarely due to the wrong registration of homestead certificates.
It is suggested that your parents contact the village committee as soon as possible. If the village Committee also finds that it is a registration error, it can give you a certificate and correct it at the town land bureau or the county land bureau.
Whether your sister's registered permanent residence is in this house has nothing to do with the area of the homestead certificate.