Generally speaking, this is something that an experienced GM can handle in session zero. An important part of session zero is establishing expectations for the style of game to be played: Things like “are the player characters friends?” “Is PvP encouraged or discouraged?” “Do I as a DM want the characters to stick together?” etc etc.
Generally when running DnD, I request of my players to design characters who:
Have a disposition to get along well with their companions. (this can be for any reason: because they’re like that with everyone, or because they’re loyal to the group, or because they view it as useful to have some friendly scapegoats nearby or any other motivation.)
Be the kind of person who will go on adventures and take risks. (This can be because they’re a daredevil, or because they’re desperate, or because they’re devoted to their duty, or any other motivation.)
Fundamentally, most DnD games are the story of a group of friends going on adventures together. If your DnD game is the story of a group of friends going on adventures, then it’s extremely beneficial for your players to build characters who will be friends, and who will go on adventures. Together.
