In case you needed any other indication that model sisters are trending right now, Balmain's fall campaign has landed and features Kylie and Kendall JennerJoan and Erika Smalls and Gigi and Bella Hadid, all shot by Mario Sorrenti.
It proves that palling around with Olivier Rousteing (and perhaps inviting your sister along) can lead to more than just runway appearances
In a statement released Thursday, Rousteing explained that the intimacy captured in Kim Kardashian and Kanye West's Balmain campaign for spring 2015 inspired him to keep featuring familial relationships. 
This season’s Balmain campaign was inspired by a brief, key moment that happened while we were shooting our last campaign. While I watched Mario capture a kiss last fall, I was struck by the love and emotion that I was witnessing in front of me. Starting with a determination to once again focus on the beauty of an intimate connection, my team and I quickly concluded that a celebration of the unique and unconditional love of siblings is a natural progression from the spirit of last season.
Who better to follow Kardashian and West than the young Jenner sisters? This marks a high-fashion debut for Kylie Jenner, who has so far stayed clear of modeling gigs — West's Adidas show and her (and her sister's) collaborations with Topshop and PacSun notwithstanding. 
Joan and Erika Smalls for Balmain fall 2015. Photo: Balmain
Joan and Erika Smalls for Balmain fall 2015. Photo: Balmain
Joan Smalls' sister Erika is also more a novice in front of the camera. The self-described social entrepreneur has appeared in at least one editorial with her famous sister, however, in Vogue's August 2012 issue. 
A representative for Balmain confirmed that the Hadid sisters and Armando and Fernando Cabral were also photographed for the campaign. We will update with those images as they are released.