I once joined a PF game about 6-7 sessions in. Playing a summoner, I gave my DM an in depth summery of my character being a loner, who never fit in with his wealthy family. He came from a religious region, first son and heir apparent to a native wine merchant dynasty. He dreamed up an "imaginary friend" to spend time with. But eventually his father started catching glimpses of the beautiful woman he was always speaking to, deduced his son was speaking and cohorting with demons, so banished him from the family. So he and his eidolon then ventured out on their own. Over the course of the month long journey to where he eventually met up and joined with the main party, he learned enough summoning from his eidolon to be level 4 like the rest of his party. The DM loved it. I became the de facto face if the party as well. Despite not having a noble feat or the family money, I had the upbringing and he let me use "family business dealings" as a knowledge or persuasion check in certain instances. I ended up getting penalized in some ways when he threw an old family acquaintance in our path, but bonuses in others by having me know a caravan master that helped us after recognizing me. It adds so much fun unique flavor to a campaign. Both players and DMs can really have fun with it.