PARIS — Ben Mendelsohn and James Frecheville, two of the topliners in 2010 breakout Australian thriller “Animal Kingdom,” have joined the cast of Anne Fontaine’s untitled English-language debut, which starts to lense Wednesday.

Aussie up-and-comers Sophie Lowe (“The Slap”) and Xavier Samuel (“The Twilight Saga: Eclipse”), and vet thesp Gary Sweet (“Small Time Gangster”) also feature in the cast.

As previously announced, Naomi Watts and Robin Wright topline in the Australia-set drama romance, which is based on Doris Lessing’s novel “The Grandmothers.” Watts and Wright star as two lifelong friends who embark on a forbidden and passionate affair with each other’s sons.

British scribe Christopher Hampton, whose credits include “Atonement” and “Dangerous Liaisons,” penned the adaptation.

Pic is produced by French shingles Cine@ and MonVoisin, and Australian shingle Hopscotch Features, which is owned by eOne. France’s Gaumont is a co-producer.

Gaumont’s international sales team, headed by Cecile Gaget, will be shopping the pic to buyers at Berlin. Gaumont started pre-selling the pic at the AFM, and has already closed Switzerland (Pathe) and Canada (Remstar). Gaget said her team was in discussion with Italian and German buyers.

Hopscotch will release the pic in Australia.

Fontaine’s 2009 Audrey Tautou starrer “Coco Before Chanel” was nommed for one Oscar and four BAFTAs.

John Hopewell contributed to this report.