The quote above is exactly what Yoshi-P explained in an interview a few months ago when it comes to NPCs from MSQ. Players will get very attached to certain characters, and if they die, well, Yoshi-P and his crew better hide. As much as I really want to marry Ser Aymeric, it's never going to happen because of story plot reasons XD (However, since Yoshi also stated that it's the player's choice to decide on who they fall in love with and what kind of relationship they have, *coughsaymericandrenareacouplecoughs*)
As for us marrying our retainers, eh I don't know. I never had that kind of feeling towards my retainer.