13. Emily and Zooey Deschanel
Okay, Zooey Deschanel MIGHT look more like Katy Perry than her sister Emily Deschanel. And she probably acts more like Katy, too.
14. Maggie and Jake Gyllenhaal
If we hadn't seen Maggie Gyllenhaal breastfeeding her tot, we'd definitely be convinced she and brother Jake Gyllenhaal are the same person.
15. Alex and Emma Watson
If Harry Potter directors had decided to take creative license and make Hermione Granger a boy, Alex Watson could've played the part for sister Emma Watson.
16. Ashlee and Jessica Simpson
Another dynamic sister duo, Jessica and Ashlee Simpson definitely look like family!
17. Mary Kate and Ashley Olsen
Mary Kate and Ashley Olsen have definitely been fooling us all this whole time.
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