@Simtown15 - y'know...there's three words for that: "That's life". You know...if someone put their own sims in a world that they created, they probably meant for others to play with them. It's the same as playing with EA created sims. Someone created the sims that we think came with the game. Do they feel like we should play their story the way they thought it should be?
To take a tidbit from real life. What about our significant others? What about their lives before they met us? It's not like their life was a blank slate before they met us, right? Should we not date them because of it? Frankly, my wife's ex-boyfriend...lost her to me, because he wasn't willing to be that guy for her. I was...and I won out. C'est la vie... There are winners and there are losers. He lost, I won.
As far as the sim is concerned, if they didn't want others to develop their own stories around that particular sim, then they wouldn't have volunteered to give the sim to world developer or tossed them in as a world sim.