HITC Sport understands duo are tracking Fulham attacker on free transfer.
Williams is out of contract at Fulham next month and looks set to leave Craven Cottage this summer.
Williams, who made his debut for Fulham in August 2014, is highly regarded at Craven Cottage, but has found himself down the pecking order in Slavisa Jokanovic's first-team plans and with the club winning promotion to the Premier League, he was unlikely to break into the first-team.
The 22-year-old spent the second half of this season on loan with Scottish Premiership side St Johnstone after missing most of the first half of the campaign through injury.
Williams made 11 appearances during his time at St Johnstone and he is ready for a new challenge in search of regular first-team football next season.
Williams, who was a member of Chris Coleman's Wales squad for at Euro 2016, has also had loan spells with Gillingham and MK Dons during the last couple of seasons.
A number of clubs in England and Scotland have been monitoring Williams' situation, but Barnsley and Rotherham are leading the chase for his signature.
Rotherham are looking to strengthen their squad sufficiently after winning promotion back to the Championship, while Barnsley are aiming to add to their attacking options as they look to win promotion from League One at the first time of asking after suffering relegation this term.