Williams, 22, has been linked to Barcelona for a year and was close to joining the team last summer but decided to stay at Athletic Club.
Barcelona's sporting director, Deco, recently met with Williams' agent, Felix Tainta, according to a report.
Yamal's post sparked interest in a potential link-up between the two players at Barcelona.
Other clubs, including Bayern Munich, Chelsea, and Arsenal, are also interested in signing Williams, but he prefers to stay in Spain.
