In California, the age of consent is 18. That means that anyone under the age of 18 cannot legally consent to have sex. Thats true, even if both parties involved want to have sex. In the states eyes, anyone under the age of 18 lacks the capacity to make an informed decision.

Can a 16 year old have a relationship with a 18 year old?

Technically it is legal for someone under the age of 18 to have a dating relationship with an adult or another minor, as long as no sexual penetration occurs. Also, it is not legal for the 18 year old to have sex with the 16 year old.

Can a 18 year old kiss a 15 year old in California?

Kissing is fine. Anything more could be trouble. Sex is definitely out as that is statutory rape even with consent. The parents could agree verbally and then change their mind.