Beyoncé & JAY-Z Have a 'Small Celebration' in Europe for Twins' First Birthday: 'They're the Cutest'

"Everyone says they can't believe how quickly the past year has gone," a family source tells PEOPLE of Beyoncé and JAY-Z's twins Rumi and Sir

Beyoncé and JAY-Z had a low-key but totally perfect way to mark twins Rumi and Sir‘s first birthday!

“They had a small celebration in Europe. It’s crazy that Rumi and Sir are already 1,” a family source tells PEOPLE of the Carter babies, who were born on June 13, 2017. “Beyoncé’s mom [Tina Knowles Lawson] is traveling with the family and was, of course, there for the celebration. Everyone says they can’t believe how quickly the past year has gone.”

The source adds, “They’re the cutest and doing very well. Beyoncé and Jay seem happy.”

Amid their sold-out On the Run II Tour, the proud parents have been on the road with their children, including 6-year-old daughter Blue Ivy, who was also at the twins’ celebration.

“She is a very sweet big sister and helps out with the twins,” the source says of the little girl. “Blue is doing well too. She has tutors so she can keep up with school work. She will get a break over the summer as well. She does well with all the traveling.”

As the family of five embarks on the many European stops, including London on June 15 and 16, the Carters are looking forward to a great summer.

“They are excited about the tour. It’s, of course, a lot of work, but this is what they love doing,” the source says.

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On Wednesday, Beyoncé gave a special shout-out during the Etihad Stadium show in Manchester, England, expressing her love for Rumi and Sir on their first birthday.

A fan Instagram account showed the mother of three wrapping up “Young Forever” by smiling at JAY-Z and saying into the microphone, “Happy birthday to Sir and Rumi. We love you.”

This isn’t the twins’ first mention in their parents’ new concert tour.

The duo made an appearance in a photo during a family collage projected at the kickoff show in Cardiff, U.K., during a montage for what appeared to be a vow renewal ceremony.