Okla. Stat. tit. 25, § 1502.5

A. The Commission may join a person not named in the complaint as an additional or substitute respondent if in the course of the investigation the Commission determines that the person should be accused of a discriminatory housing practice. B. In addition to the information required in the notice pursuant to paragraph 3 of subsection F of Section 8 of this act, the Commission shall include in a notice to a respondent joined pursuant to this section an explanation of the basis for the determination that the person is properly joined as a respondent.