Ok i know that this was discussed before after seeing other similar games i have realised that in most of them.... you join a clan/group/guild and do quests and gain ranks and then potenitally fight other clans/guilds/ etc
This is typical and a bit boring.
So what i suggest is something a bit different.
If you have say assassins and they are fewer than 25 in number...they will be called a group.
If you have say rangers and there group is between 25-50 then its a clan.
If you have say fighters and they are more than 100 then i say its a guild.
So it would be fun to have different names for such paths(e.g fighters,wizards) and depending on their number you would have dfferent factions.
E.g there would be no factions in goups...2 factions in a clan and more than 2 factions in a guild.
E.g in the fighters guild you could have knights,barbarians,paladins. In wizards guild you could have druids,necromancers,sorcerers.
Assassins could be a clan as there would be say assassins who use throwing weapons or those who use say posion.
In guilds/clans you could solve quests which would stop the factions from breaking up as well as other outside quests. In groups you would say persuade other poeple to enter the group to become a clan and also do other external quests like actually assassinating people.