In Harry Potter: Hogwarts Mystery you can get to know many characters living on the grounds of School of Witchcraft and Wizardry. Your choice of friends does not have to be limited to the same house. You can be friends with the characters from a different house, and be hostile with your dorm mates.
The bottom right corner of the screen contains three icons. The leftmost gives you access to the friends list. Inside, you can view the list of all students you come to know during storyline missions in Harry Potter: Hogwarts Mystery. You can develop relationships only with them.
The friends list contains avatars of every encountered character, the level of friendship and the information about the reward which will be received once you develop the friendship. The character photographs will allow you to determine which house the person belongs to.
To develop a friendship, you need to talk with the given person, take part in events with him/her and play gobstones together. If you get on well, you can quickly reach new levels of friendship. Each level of friendship comes with a reward, for example reaching level 2 of friendship with Rowan yields 5 gems.
You can quickly develop the friendship by playing gobstones. Each game costs 10 coins. During a game of gobstones, you can choose one of three available answers, divided into Great, good, and bad. To win the game, get as many great answers as possible. You'll be facing 6 rounds during which you need to get three stars. Your task is to distract the other player. If you manage to do so, you'll win very quickly.