You can go horror quite easily with such a premise. Like: you get back home after a "nice" day of work and you find that your family, the kids, other half etc, they do act creepy or (worse still) slightly different from how you are used too. Strange look in their eyes, strange way of speaking, they sit in different positions at the dining table than usual and so on. We could go straightforward (body-snatchers, anyone?) or imagine an unreliable narrator (i.e.: you are the one that has changed instead of the family). Very much Twilight Zonesque, imho.