What should I do about the hardship of repeatedly purifying the house from impurities due to my father and my sister's children not taking precautions, knowing the jurisprudential rules and being certain of the transfer of impurity?

Everything touched by a person who does not guard against impurity is considered pure until impurity is established with certainty. Therefore, do not burden yourself with purifying everything your relatives touch, and consider everything pure, for the basic principle is that impurity is not transferred until you know it with certainty.