The Dunsany sisters, two significant characters from the novels by Diana Gabaldon, are getting their small screen counterparts in "Outlander" season 3.

Hannah James will play the older Dunsany sister named Geneva, while Tanya Reynolds will portray younger of the two, Isobel. It is unclear as to how they are going to be depicted in the series.

Sam Heughan, who plays the role of Jamie in the series, welcomed the new cast members, whose characters are significant in the life of his own character.

"Such a treat to be working with you... even if I am freezing my buns off in Scotland," James tweeted to her co-star, Heughan. "So honored to join this incredible cast and crew. Ready for the ride!" she said in another tweet.

She also sent love to Gabaldon,  saying that "Outlander" is "such a terrific story to tell" and thanked Catriona Balfe, who plays Claire, for the warm welcome.

"So very excited to be a part of this story," her fellow "Outlander" season 3 newcomer, Reynolds, tweeted when their casting was announced.

In the books, Geneva meets Jamie at Helwater when he serves his parole. She eventually falls in love with him and blackmails him to bed her when she learns she will be forced to marry a man old enough to be her grandfather.

Jamie had no choice and does what Geneva asks. The older Dunsany ends up with the old man anyway but discovered that she may have been impregnated by Jamie when they spent the night together.

Whether or not "Outlander" season 3 will feature this remains to be seen at the moment, though. As for Isabel, it looks like she only appears after her sister's death.

Filming for "Outlander" season 3 is well underway. The series should return on Starz with new episodes in April next year.