The Atletico Madrid attacker has announced this week he will leave the Spanish giants at the end of the season.
Barca are favourites to land Griezmann, with a willingness of meeting his €120m buyout clause.
However, ZDF says Bayern sports chief Hasan Salihamdizic has met Griezmann's sister, Maude, in Madrid. Maude also acts as her brother's representative.
Bayern already have a deal Griezmann's teammate Lucas Hernandez, who moves to Munich for his €86m buyout clause.