How to allow child accounts to "friend" each other?

[Sopha]

My two kids are part of my Steam Family. Additionally, my account has Friend status with each of them, allowing me to play multiplayer games with them. I can't figure out how to get them to be Friends with each other, however. I would like to allow them to play with each other (for games we've purchased twice or are FTP). Can a Parent account enable Friend requests between Child accounts?

[Ogami]

They should just be able to friend each other by sending out a friend invite. Either by visiting the other kids profile and clicking " add as a friend" or giving them their friend code thats available under "Friends" "Add a friend" in their Steam client with no input from you at all.
Mind you, at least one of them need to have an unlimited account, meaning they have to had spend 5 bucks at on the Steam store.
You can only send out friend invites if your account is not limited (level 0) and if both accounts in question are limited there is no way for them to add each other as friends.

[fredr]

If the child accounts have not spent any money, they can still friend each other by going to the Add a Friend page and giving the quick invite link there to the other account.