The 23-year-old singer and 25-year-old actress attended Jeremy Bieber's nuptials to Chelsey Rebelo Monday in Jamaica, according to E! News.
"Selena and Justin flew overnight from Dallas to Jamaica for Jeremy Bieber's wedding on Monday," a source said. "They spent the day with Justin's family at a resort catching up and getting ready for Jeremy and Chelsey to get married."
"Selena was very comfortable with Justin's family," the insider added. "She was hugging some of them and seemed right at home."
Rebelo posted a photo Tuesday on Instagram that shows Bieber applauding as she and Jeremy share their first kiss. Bieber, who dressed in casual pink shorts and a white shirt, appears to have served as a groomsman.
"Yesterday was the most amazing day ever. I married my best friend!" Rebelo said of Jeremy. "I love you!"
TMZ reported Bieber and Gomez were "inseparable" during the wedding. The couple were spotted embracing and cuddling during the reception.
Bieber and Gomez reconnected in October after splitting in 2014 after several years of on-again, off-again dating. Entertainment Tonight reported Tuesday the pair "are going strong" and "together all the time."