I want to inherit custom fields from an organization contact to an individual contact with a relationship. I'm asking if it's possible to do that or not.
Welcome to SE. There is no inheritance of custom fields via relationships.
I'm not aware of an extension that does that but it would be possible to write one that copies fields from an org to an individual based on a relationship and keeps them updated if the org fields are changed.
Alternatively you might be able to achieve what you need with CiviRules