The pair – who played Osha and Talisa on the HBO phenomenon – take centre stage in the bittersweet drama Anchor and Hope, playing a same-sex couple.
The film is about two women living on a narrowboat in London; one of whom reveals that she wants a baby.
When their best friend Roger visits from Barcelona, all three of them begin to toy with the idea of embarking on parenthood together.
“Where does the desire to have kids come from? I am thirty, the age that biology obligates you to confront one of life’s most important questions: Do I want to have kids or not?” director Carlos Marques-Marcet said, according to Gay Star News.
“And another question comes with it: Is there any other way of having a family that differs from the image I have known throughout my life?”
Anchor and Hope was debuted at the London Film Festival last October, and will soon be released to cinemas.
It received mixed reviews upon its release, with Screen Daily saying: ”While Anchor and Hope isn’t subtle in its approach, it is nuanced in its emotional and naturalistic in its look and feel.”
HeyUGuys, meanwhile, wrote in a three-star critique: “The long shots of canals and rivers are just gorgeous and this unconventional setting really is stunning to watch.
“It’s just a shame the characters themselves weren’t so engaging.”
Before playing Osha in Game of Thrones for 16 episodes, Tena will be best-known for playing Nymphadora Tonks in the Harry Potter series.
She portrayed the character four times – in Order of the Phoenix, Half-Blood Prince and both parts of Deathly Hallows – between which she starred alongside Luke Treadaway in You Instead.
Chaplin, meanwhile, is signed up to star in Avatar 2 and 3, currently in production.
On television, she’s also appeared in Black Mirror, Inside No9, Sherlock and Spooks.
Game of Thrones is currently preparing its final season, scheduled to air on Sky Atlantic in the UK and HBO in the US at some point in the first half of 2019.
George RR Martin, whose books inspired the whole thing, is still working on his next instalment, The Winds of Winter, with no release date currently set.
Anchor and Hope is out on September 28.