The Mare of Easttown star shared a pair of behind-the-scenes photos with her older sibling whose heavy metal and alternative punk band had just wrapped up a show.
In the shots, Travis showed off his heavily tattooed body, long hair and makeup as they chatted with a drink in hand.
WATCH: Kevin Bacon and Kyra Sedgwick perform adorable duet
They both wore black T-shirts and behind the eyeliner and body art, fans could see the resemblance between the two.
"He kinda looks like you Sos," wrote one of her social media followers before clarifying, "in the best way possible".
Sosie captioned the supportive post: "@contracultofficial was mesmerizing through and through and the fact that venues smell the same as always is ever so comforting."
Sosie shared her support for her brother with a backstage photo
Travis certainly looks very different from the blonde-haired little boy he once was and often ramps up his extreme appearance further when he takes to the stage.
For fans of the band, Travis' appearance isn't so shocking, but many of Kevin and Kyra's followers may not know what their son does for a living.
In addition to being a singer and programmer for the band, Contracult Collective, he plays guitar for black metal band, Black Anvil. He's also an audio engineer and songwriter.
Travis sports an extreme appearance on stage with his band
Kevin and Kyra have previously spoken about their children's desire to go into their chosen careers and said they did try to sway them from working in the spotlight due to the intense pressures.But ultimately, all they want is for them to do something they love.
"Honestly, I really just want them to be happy," she said. "It is difficult being in this business, knowing how hard it is even when you're successful.
Travis' childhood blonde locks are now nowhere to be seen
"The hurt, the rejection, the insecurity of thinking you're never going to work again... I don't want that for my kids."
Kevin added: "And you want your children to live a life with as little struggle as possible. You never want bad things to happen. But of course, that's just not possible."
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