Might have a fix,
I had this issue then did 2 things:
Firstly, accepting this quest may push you over the companion limit, so tell one of your companions to stay in the village, Top Right of the screen when in the village menu, You can check your companion limit by going into the Clan Screen by pressing L by default.
Second, i placed the family member at the bottom of my companions in the party screen
Edit*
Seems to also only work in daytime
I'm not certain if this fixed it, or it's just random, but it's something to try at least.
Let me know if it works if you try it, thanks.