I plan to ask my family to clean their home before we have out family gathering there.
Why would you ask them to clean their house before the family gathering?
The house is very dirty and it won't make a good impression on the rest of our family.
I'm sure it's frustrating that your family wants to hold a gathering in an unclean house. Talk to them and explain the importance of having a clean home. Offer to help them clean so that they don't have the entire burden of the house cleaning.
I want to ruin the family gathering. This way the family will be ashamed and not have any future family gatherings.
Well the family gathering will probably not go as well if the house is not cleaned. You should probably help clean the house, as not cleaning it will probably cause your family to be ashamed.