Gravatar bears several affiliations of note.
First, of course, is his fiancé Aohdan Darragh, also known as the superhero Omnitone. When the Irish mutant arrived in Paragon City fresh from County Antrim, Gravatar took him under his wing, serving as his official mentor via GIFT. It was during that time that the pair fell in love, and once Aohdan finished his mentorship and became a fully-fledged registered superhero in Paragon City, he proposed to Gravatar, and the two are now enjoying both a happy engagement and a solid partnership in the field.
His closest friends and allies are the Praetorians Tien Tamari-Mizu and Daniel Davisson, former Resistance fighters who, like Gravatar himself, transitioned to Primal Earth from their native Earth. Tien served as a mentor for Gravatar when he arrived from Champions Earth, teaching him how to better utilize his control of gravity to support his teammates in combat situations. The pair of them remain close with Gravatar, and are often his first call when he requires assistance in the field. He even maintains a permanent wormhole from Gravtopia to the mountaintop chateau where the pair of them live.
Gravatar also maintains close ties with several of his former teammates within the Global Defense Force: Citizen Thirteen, Crowning Glory, Starspark, Elycion, Areus, Farside, Nitroburst, Ultrastar and the alien entities Hugs and X. He often assists them with field work, though he himself chose to resign from the GDF in order to focus on his work with the Portal Corporation, and counts them among his closest allies on Primal Earth. He also bears an unusual but close friendship with Mu'Sekhmet, one of the Mu Guardians from the Rogue Isles, as well as her concubine Dominic Balthazar Ashera. This has raised some eyebrows amongst his colleagues in Paragon City, but Gravatar pays these concerns no mind.
Professionally, Gravatar is most affiliated with the Portal Corporation. He recently accepted a full-time position with Portal as a field operative, and can most often be found assisting them at Firebase Zulu in the Shadow Shard, due to his unique ability to operate in that dimension's gravity without detriment. He has also been a member of the Northern Stars and the Global Defense Force, as previously mentioned, and also maintains contacts with some of his former co-workers at the Paragon Times.
As of late, Gravatar has begun mentoring Massifist, another gravitikinetic mutant like himself, but one who has taken a pacifistic approach to hero work.
On Champions Earth, Gravatar was a member of the Forces of Nature (Undertow, Earthmover, Windshear, Sunscorch and the team leader Plasmus) in good standing, until their untimely demise at the hands of the supervillainess Gravitar. He was also closely affiliated with the Champions Earth versions of Citizen Thirteen, Starspark and Elycion, working with them via PRIMUS on several high-profile cases.
Beyond these ties, Gravatar is in good standing within the superhero community of Paragon City, and his reputation has even begun to extend to other worlds throughout the multiverse as his work with the Portal Corporation has taken him to other worlds and other dimensions.