I find this a very slippery slope.
I absolutely offer unsolicited advice to my Dad, who quite appreciates it actually. Sometimes I offer it to Greg too - who offers unsolicited style advice right back I might add :0).
But for the rest, I don't say anything at all unless I am directly asked a question by a family member or friend. Then I'll answer truthfully and tactfully as best I can.
What do you do?