The characters who team up in this group are a doctor (Jean), his wife who is also his nurse (Eberle), and their two children (Halley & Emmy). In the final dungeon, with you controlling Jean, they take the fifth path and face a two headed serpent that splits into six copies and changes color the more you kill. Said boss is the reason for the team name, since I read about it beforehand and learned it was quite an irritating fight. Ironically, I beat it in two tries my first two playthroughs (and only lost due to stupidity in firing my scalpels the wrong way and not healing).
Jean comes into your group pretty late, so it's hard to gauge his personality. He seems to take the longest out of his family to express any real Trust in Ark, and appears to be a calm, cool and collected individual. However, according to Halley during the "fake Jean" segment, he would never refuse to treat someone, no matter what the risks to himself or his family. It's Jean who treats the badly injured Telmia in the next-to-last regular dungeon, as well as a certain end of the game near-death situation. But the one thing we know, without a doubt, about Jean is that he is extremely devoted to his family.
Since Jean comes in real late, Eberle plays the role of healer for your party for much of the game. She's just as calm as her husband, however since her abilities aren't as good as his, she sometimes feels unable to fully help out. Like Jean, she is incredibly devoted to her family and is relieved to find out that Ark and Ivy took care of her kids.
Halley is the more adventurous of the two siblings, always looking for excitement. He seems pretty geared up in the beginning, and when he asks if they'll see any CIMA it's almost as if he wants them to appear. There were never any questions asked about helping Ark with item finding and such, in fact Halley suggested the treasure hunting and comments his readiness to go over several of the rickety bridges you find in the game. He looks up to both Gate Guardians, seems to hero-worship Ark, and wishes to grow up to become a Gate Guardian.
While Halley is considered extremely brave, Emmy starts out as a crybaby who needs prodding from her big brother to even move forward in a dungeon. However, when she and Ivy are separated from the others, the older girl literally slaps some sense into her, and she begins to try to be brave. From then on out, Emmy is just as capable as her brother in going through the dungeon hazards in order to find hidden treasure or hit switches over broken bridges. She also hero-worships Ivy, much like her brother does to Ark.
Most, if not all, of the group dynamic stayed between the members of the family. When it did stray, it was mostly from the kids and their admiration of the Gate Guardians, as well as their bravery to go across broken bridges. The rest of the time, their scenarios are about the closeness within the family.
All ages taken from the Character Books in the Blue Creek from both CIMA: The Enemy and Frontier Stories. Starting Trust is the Trust held by the pioneers at Game Start/After Jester's Death.