In promos for “Abby & Brittany,” premiering Tuesday on TLC at 10 p.m., I saw what appears to be a young woman with two heads, riding a bicycle.

At first, I thought this was a spoof. In fact, the “docu-series” follows real, conjoined twins, who have separate heads, lungs and hearts but share a body. Is the show exploitative? Educational? Inspirational?

For guidance, I turned to Alice Dreger, professor of medical humanities at Northwestern University’s Feinberg School of Medicine and author of “One of Us: Conjoined Twins and the Future of Normal.” Yes, it’s exploitative in a way, Dreger says. The twins put themselves on display; the viewer is a voyeur.

Then again, the twins consented to the series, helped shape it and are being paid. “That’s cool,” Dreger says.

If you tune in, you’ll find Abby and Brittany are remarkably normal. They eat fondue, shop, celebrate their 22nd birthday. “They refuse to be objects of pity,” Dreger says. “They are shameless in the positive sense — without shame. And that helps everyone.” How can anyone be embarrassed by a physical defect after watching these intrepid twins, who draw inevitable stares, yet go out and about, living ordinary lives?