Oh, gosh, yes, I get attached to my sims, to the point I've cried when those special ones die. And, yes, I do know what you're talking about, OP, about how sometimes your sims take on lives of their own. I've had two in my ID that really broke the mold and came alive, Merida and her son, Malik. I won't go into details (bc I plan on posting the dynasty soon) but Merida was a fun, active, happy momma bear and her son was a determined, Insane little genius who brought a lot of comic relief and light to the family for most of his life that I couldn't help falling in love with them.