Check the banner of the game and listen to Sven saying you're going to meet your companions at the very early beggining of the game. I don't think you'll find other "companions" during the rest of the game exept what they called followers.
We have to hear more about them but I think they"re not going to act like true companions (I bet for followers for specific quests or followers staying in your camp such as a healer, a merchants, a side quests giver, a guideline to the story or temporary important NPC...)
In the alpha versions of Divinity Original Sin 1, Madora and Jahan were not in initially, nor were Walgruff and Bairdotr. In Divinity Original Sin 2, Beast and Fane were not in until the full release of the game. Not having all companions in this pre early-access version does not mean that there will be no other companions in the starting area.
In fact, I'd really hope that there are more companions around than you can take with you, so you can have a party generally aligned instead of being forced to go half-evil/half-good.
