They were not and never would be quite human, and they knew that Sarah Jane wasn't their biological mother. Still, it was harder to lose her than either of them had ever thought - not that they tried to think about it, but there were more close calls every year, and even though Luke asked, finally, if she would slow down, they knew Sarah wouldn't stop trying to save the world until she had to (that conversation had been awful, and only a week later she'd been gone, out in a blaze of glory, like they'd all suspected would happen, and neither of them were at all surprised).

They carried on her legacy the best they could - no weapons, and they were always Smiths, even if the Doctor looked sad when he saw them nowadays - it was what she would have wanted, and how she had raised them; they were more human than not thanks to her, and it was a badge they both wore proudly.