ERC is not available to owners or relatives of owners.
It seems that it is available to owners and owner's spouse of a corporation just not to other relatives
https://www.irs.gov/newsroom/covid-19-related-employee-retention-credits-determining-qualified-wages-faqs59. Are wages paid by an employer to employees who are related individuals considered qualified wages?
No. Wages paid to related individuals, as defined by section 51(i)(1) of the Internal Revenue Code (the "Code"), are not taken into account for purposes of the Employee Retention Credit. A related individual is any employee who has of any of the following relationships to the employee's employer who is an individual:
A child or a descendant of a child;
A brother, sister, stepbrother, or stepsister;
The father or mother, or an ancestor of either;
A stepfather or stepmother;
A niece or nephew;
An aunt or uncle;
A son-in-law, daughter-in-law, father-in-law, mother-in-law, brother-in-law, or sister-in-law.
In addition, if the Eligible Employer is a corporation, then a related individual is any person that bears a relationship described above with an individual owning, directly or indirectly, more than 50 percent in value of the outstanding stock of the corporation.