It's mainly through someone's friend list I believe. When you hover over the game on the PS4 desktop, it shows beneath the game who all on your friends list is currently playing it. Beside the person, it says Join Session. From what I've heard, people can click Join Session on that person and it automatically puts them into that person's group. Not sure about randos.

Ok, because we were irritated enough, we tested it tonight. Here's what we found.

Person clicks the Join Session button of person who is logged into the game, which starts their game. They finish logging into their character, and then they get a group request from the person whose session they have joined, which they can then accept and group with that person, all without that person who was already logged in getting any notification of any of it. Seriously, it sends them a group request from whichever of us they clicked Join Session on. No input from said person. No notification either of us sent a group request we didn’t actually send. This feels like it’s not working as intended. Or that there should be some way to stop it from happening, anyway. Sometimes, you just want to be alone (or with your spouse)!

The only way I have found to stop it is to set my online status to offline, so there’s no Join Session button to click. At least until we can find a polite way to inform all our friends (and our friends' friends) that clicking that sends a group request to them we didn’t actually send (they may not know what’s what’s happening), that it’s sort of rude to not ask first, and that it makes us cranky. Or maybe we'll just never show as online again. LOL!

So now we know! Thanks for pointing me in the right direction!

Is the vote to kick someone out of a group only available in dungeons? If not, both you and hubby could vote to kick whoever from your group. It really doesn't seem right that another person, friend or not, can just glom on to your group without your permission. Then you find yourself awkwardly having to ask them to leave. Another solution, inconvenient but possible, is that whoever has the crown can disband the group. Then just reform the group with the two of you. If the other person had to click "join session" while logging in, they would have to log out and back in to do it again. After being forcibly removed by disbanding, seems like they would just go away and play on their own. If they did it again and came back, you'd probably have to move into offline mode to get rid of them.

Have you ever thought of making your own guild for just the two of you? It involves some work but can be done. To have guild bank and I believe chat requires ten members. You each would have to make four new gamertags and make a character on each gamertag. Add the characters you play plus the alternate accounts to the guild. Don't let anyone else join. Then you can talk in your guild chat without fear of other people butting in. If you decided to group as well, just log out of the group chat but keep yourselves in the guild chat. Then if someone did pop up in your group again, they couldn't hear you talking in your guild chat. It's a bit of work but you seemed annoyed enough by the newcomers that it might be something to consider. The 500 space guild bank would be a great place to share things between you as well.

I envy you. My BF and I want to play together but as of yet don't have funds for a second Xbox.