I'm not sure what exactly this makes the scientist to Grace in terms of what word to use with the least amount of confusion, but they are indeed blood relatives.
Mild spoiler warning for the remainder of this commentary if this is your first time reading EGS.
I'm pretty sure I was going somewhere with some sort of negative side effect of being part Lespuko that could potentially nerf Grace (in other words, lessen her shifting abilities). I wound up not doing this for several reasons, so a fair amount of Nioi's speculation about Grace doesn't really go anywhere. This is a bit annoying to me, but hey, she's capable of being wrong, and it beats the alternative of stubborningly sticking to it even if I decided it was a bad idea later.