CHICAGO—Noting that the siblings have “an adorable back-and-forth,” sources confirmed Monday that 22-year-old Dan Callan and his 19-year-old sister Autumn have “pretty good chemistry.” “Anyone who knows the Callan kids notices how they really seem to vibe each other. They talk for hours, and since they have a ton in common, the conversation is effortless. Oh, and he calls her ‘Baby sis’ when she says something clever or he wants to tease her. Oh my god, it’s really something,” said Callan acquaintance Jeremy Ryan, who claimed he could “sense the sparks” between the two when Dan playfully pinched his sister’s arm or Autumn licked her finger to give Dan a wet willy. “They have a super flirty rapport, constantly giggling and referencing private inside jokes. They know each other intimately enough to finish each other’s sentences. And Dan just lights up when he sees Autumn. The long hugs he gives her, I tell you, it’s something to see. And she doesn’t hide the fact she loves it, either.” At press time, sources reported feeling chills up their spines as they watched the two share a kiss goodbye.