Cannot Join a Steam family

[MasterEND]

I've added my brother in law to my family, and he can't join my group and vice versa.
The message that pops up reads the following;

"Failed to accept the family invite. You are ineligible to join this Steam Family at this time, as your Steam activity doesn't indicate that you are in the same household as other members of this family."

and me and my friend are from the same country and country store , and region is the same

[Directed By Michael Bay]

yeah me too. what can we do now?

[Blizzard]

Also happens to me

[Ell Ethet]

you need to log in to an account of one of the members of the said family group in your device. i got the same error and doing so fixed it.

[76561199293274634]

what can we do now?