how many people can be in a party

i've been looking around and cant seem to find an answer, me and some friends want to group (3 of us) but only 2 of us can be grouped at a time (wont let third guy join says merged group will be to big) i'se seen screenshots with at least 4 people in a group and i think it would be kinda stupid to only allow 2 people in a group at a time, are we doing something wrong here?

It increases as you progress. When you make it to post-searing you'll get 4 people in a party, then 6 at the shiverpeaks, and I'm not sure when 8 people parties open up

no
after you are out of the tutorial you can have larger groups as you progress

wow that was fast, thanks a lot for the help.

8 at the dragon's lair (that's after ascension)