Beneath the Swirling Sky by Carolyn Leiloglou
After a troubling experience, Vincent wants nothing to do with art during spring break with his sister, Lili, at their great-uncle's home. However, when Lili disappears into a famous painting, Vincent discovers that his family is part of The Restorationists, a secret society that protects artwork and can travel through it. With Lili's safety at stake, Vincent must confront his family's secrets, team up with his cousin Georgia, and face a new adventure where paintings serve as portals to danger.