Well if you a) give him a limited user account and b) just enter this line in the HOSTS file 127.0.0.1 youtube.com. I believe that by blocking the domain and not the full url that should block even the https linking.
Or you could try blocking the IP addresses for youtube (see the list below) as that shouldn't even consider the https aspect.
66.102.9.91 66.102.9.93 66.102.9.190 66.102.9.136
Thanks everyone for your advise
It is better to smoke cocaine than watch Youtube
It is highly addictive for some
I am not allowing my brother to watch Youtube because he gets addicted. He tells me he need 1 hour for Youtube, but this 1 hour become 2 then 3 and 4
I don't want him to spent much time watching weird clips ( most of Youtube is Junk)
@ David
I have already given him a standard account
I tried to block HOSTS file 127.0.0.1 youtube.com via Hostsman but I couldn't block the https aspect
It seems starting with https can unblock most sites if the Firewall used for filtering doesn't scan SSL
There is an option in K9 Web Protection for this and I found success with it
EDIT:
It seems I can unblock some banned sites in this country by starting the web address with https if the web site uses SSL