How to evict my son that is 35 years old a and lived in a trailor of mine for the last 12 years and never paid any rent

What state is the trailer in?

Familial relationship has no bearing here. So I'm moving this from Family Law.

ANY question on law needs to include your general locale as laws vary by area. You have to follow the procedure for your area.

Was there an agreement to pay rent? If not, then you can't use non-payment of rent as a reason. So you give him written notice to vacate (the deadline depending on local laws). If he doesn't leave, then you go to court for an eviction order.