No it isnt illegal unless you have any kind of sexual relationship. Just petting could result in criminal charges for the 18 year old , and landing him on the sex offender registry for life.

Can a 18 year old date a 16-year-old in Illinois?

The statutory rape laws, or the age of consent laws, in Illinois revolve around the presumption that anyone under the age of 17 cannot consent to sexual acts. For example, an 18-year-old high school senior having sexual relations with a 16-year-old high school junior could be found guilty of criminal sexual abuse.

Can a 18 year old date a 16-year-old?

While in many circumstances it is perfectly legal for an adult to have consensual sexual contact or intercourse with a 16-year-old, there are some circumstances where it is not. Most often, it comes down to the nature of the relationship between the two individuals.