It would be an interesting change of pace if Sera had well off (for elves anyway) loving parents and had no real tragedy in her life. Having someone normal...ish could be fun.
You know what would be really weird? If both of her parents will still alive, relatively happy and even has siblings that she's on good terms with. No rape, no Alienage purge, just a decent childhood. There are ways to make her interesting without resorting to some of the awful levels of tragedy we've seen from our companions' pasts so far.
Ah, it's nice to dream. 
I would love a party member who has lived a charmed life who suffers in some way after joining the party. A noble or something.
I have a feeling Vivienne may qualify. Her life, especially by mage standards, was quite charmed. She had the ear of the Empress of Orlais, was First Enchanter, and had more power than most nobles. After Asunder, well...so much for that. I think Sera and Varric are filling the role of "every man" in this adventure.