You can follow the conditions of applying relative visa and get more information about Iran visa on this page.
The Iran relative visa can be issued to foreign nationals whose relatives are an Iranian. In order to issue for this type of visa, The Iranian relatives of applicant, who hold the permanent residence of Iran, must refer to the Ministry of Foreign Affairs Consulate in Iran and submit their application to the department of relative's visa. The host must prove the kinship between applicant by providing documents. The host can refer to Iran consulate in other countries if is not resident in Iran.
You can get more information about extension of Iran visa, terms and conditions and follow other Iranian visa information including tourist visa, business visa (corporate visa), multiple entry visa and airport visa on Hipersia website as well.
“Oh! Squander not this breath that Heaven hath lent thee, Nor make too sure another breath to borrow!’” Khayam