As soon as possible, consent can affect more than just sexual relationships and building the skill of kids sharing what they do and don't okay is a good skill to have
So many children are not taught how to say no to an adult, they are told to listen to what adults tell you. It is exceptable to say, " I do not want to hug you."
Consent is important to understand from childhood. It should be a normal part of life, an expectation not exception. But it needs to be both ways. Our right to consent and other peoples autonomy and right to consent.
Consent should be respected at an early age even before the child can talk. Show respect for non-verbal signs of consent. Show the child that you will not force hugs or kisses. Begin to talk about consent and what is not ok and the rights very early on. Be open, age appropriate and create an environment where your child can talk to you about anything.