I couldn't say whether or not any YouTube or Twitter users have reported concern but I did hear audio last week of one of Greg and Kai's neighbours' call to police, requesting a welfare check on Kai. Apparently this woman, a number of other neighbours, parents of kids in the same play group as G&K's 2yo, and parents who take/collect their kids from the same school as G&K's son, were all concerned they'd not sighted Kai at all over weeks prior to her call.
The neighbour reports that it's usual to see Kai around the home, at play group, and that she normally drops the son off at school and collects but that only Greg had been seen doing this for weeks. She says that hearing verbal conflict between the two, and seeing Greg yelling and "pushing" Kai in the driveway had contributed to her concerns when she and the others discussed how long it had been with no sight or sound from Kai.
Hearing the call, the impression I have is that Kai is cared about and well-liked in her local community, and detected no negative feelings about her. Greg... the neighbour seemed, I'll say "carefully neutral" to "restrained" when mentioning him. But that's just my impression.
*Apologies for not having a reference link, I heard this last week on one of the many videos re: Onision, and fcked if I can remember which video, or channel, and YouTube 'watch history' seems to have auto-wiped some days' viewing also. [ Hence this autistically long post attempting to give every other detail]