family
I've seen this dealt with in a number of ways.
1) My way. I don't teach children so parents aren't a factor
2) One Dojo I trained at on three occasions had a "waiting room" for parents. Between the doorway of there and the Dojo area there was a sign (like a road traffic sign) saying something like "Anybody not training must stay behind this sign and must be silent". They also had a shoe rack so parents had to remove footwear before approaching the Dojo area. Because it was a sign and not a verbal instruction it seemed to work.
3) Approach the parents in a jokey way. Say to them "There's no talking until you've been my Uke." Show them a throw and they'll soon be quiet. When I did teach children I used to run classes in a "working men's club" (I don't know if you have those outside the UK - they are like nightclubs but for old people with bingo, karaoke, and you have to be a member) using the dance floor as a "dojo". Often the parents would be watching while having a beer. Sometimes parents (of especially young children) would coach from the sidelines: "No, Callum - that's your left leg". And I would just make a joke with them, taking my belt off and saying "sorry, shall I leave?" It seemed to work!
Simon Keegan 4th Dan
www.bushinkai.org.uk