She was in some kind of e-LDR with a guy named Joel (JayDeeVA) who lived in the UK. They don't seem to have ever met offline, although I'm not 100% sure. She used to stream with him and he used to mix and edit her videos. They broke up about 10 months before she joined hololive. This is the one that showed up as "Jay" on her switch friends during the Ring Fit Adventure stream. She changed her Nintendo Account from Senzawa to Gura, but never deleted her old friends list.
About 1 months after they stopped streaming together, she started streaming with someone named BarbieSE. They seemed to have met through Dead by Daylight. She used to play with that group before she graduated as Senzawa.
Barbs is the one from Sweden, is in the Swedish military, and it's unknown if they are in a relationship. He is her only moderator on her old twitch channel.
When Gura created her official Hololive twitch channel last year, we discovered that Barbs had a founders badge, which means he was one of the first 20 people to subscribe to her.
During her WWE stream last year in August, right before the first EN off-collab, she made a strawpoll and linked to it in chat. It said that the poll was created by an anonymous user from Sweden. It could have been a VPN, or she might have been visiting there before she had to travel for the collab. There was a 48 hour gap between that stream and her appearance in LA.
When people found her steam account, she secretly created a new one and then added her brother, Barbs, and Cows(one of barb's friends) in that order.
When Gura first came back after a long ghosting period, she played Outlast on stream and was a pro at it. Barbs' friends were seen to be playing it during that time and recently, when asked if he plays it during a stream, Barbs said that he and his friends exhausted Outlast trials over the summer.
Gura's brother added Barbs on steam about one month ago. So they are definitely still playing together.
One thing to note however, is that Barbs now plays DBD with a new friend of his, a 22 year old german woman who is his new channel artist.
There are other, small things, and there's never been a smoking gun, but it wouldn't surprise me if they were together.