Yes, Jonathan Frakes and Marina Sirtis are indeed close friends, a bond that developed significantly during their time as co-stars on Star Trek: The Next Generation.
A Lasting Friendship Forged on Star Trek: The Next Generation
Marina Sirtis, who famously portrayed Counselor Deanna Troi in Star Trek: The Next Generation, forged deep and lasting friendships with several of her fellow cast members. Prominently among these close relationships is her bond with Jonathan Frakes, known for his role as Commander William T. Riker.
Their camaraderie extended well beyond the set of the USS Enterprise-D. This enduring friendship is notably highlighted by the fact that Jonathan Frakes, alongside other Star Trek: The Next Generation castmates such as Michael Dorn (Worf) and Brent Spiner (Data), served as groomsmen at Marina Sirtis's wedding. This personal gesture underscores the strong and genuine connection they share, which has continued for decades following the show's initial run.
The two actors often appear together at fan conventions and continue to engage in various projects related to the Star Trek universe, consistently demonstrating the profound and sustained nature of their friendship.