Should taxes be paid for running business out of house?

Say there are four siblings who are trying to sell a house. One sibling has been running her business out of the house for the last 18 years. However, her father was paying the taxes on the house until he died last year. 

1. Should she have been paying taxes because she has been running a profit making business from her house where she had her office and ran her freezers?

2. Should her siblings be responsible for paying taxes on the house they all inherited if she is still running a profit making business from that house?

Can the siblings report her for not paying taxes on her business out of the house all those years? In other words, can they contact the IRS and request an audit?

This is all hypothetical of course.