The 19-year-old actress, who plays younger sister, Arya to Turner's Sansa Stark in the HBO's fantasy drama TV series, took to Twitter to express her love for the birthday girl.
"Happy 21st Birthday @SophieT... Forever looking up to you, in more ways than one," Williams tweeted.
She posted an old picture where she can be seen in awe of Turner, as an actor and an individual perhaps.
The two on-screen sisters share a warm relationship and have been often seen spending time with each other off-camera too.
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