Cute couple Lena Dunham and Jack Antonoff celebrated their siblings Thursday night at the National Arts Club for a preview of the 2013 fall/winter collection from clothing designer Rachel Antonoff, Jack’s sister. The event featured a screening of “BFF,” the short film the “Girls” creator directed, which showcases Rachel Antonoff’s clothes. The film also features Dunham’s sister Grace and music by Jack, guitarist of Grammy-winning rock band Fun. Despite there being many family members nearby, Antonoff and Dunham still partook in a bit of PDA. Spies said the couple were “openly making out” while DJ Hesta Prynn spun some Usher tunes.