They can be charged with abandonment and abuse. Until the child is 18 the parents are responsible.
change the locks on the house, as ultimatum.
You can change the locks when they are out of the house. You could charge them with trespassing and have them removed by the police.
maybe send him over to a friends house or relative (that lives nearby). or just leave him at home but make sure he locks the doors and windows and stuff.
Then the parent of the 21 year old must want their kid to go to prison for some reason.
No, but you can do it once you turn 18.
Changing the locks on the doors is a little harsh. Has all else failed? Of course you can change the locks on your house doors and lock her out. This could create a life long rift in your relationship. If you can afford to pay first and last month's rent. Offer that. If she refuses, then change the locks. You have done what you could to prevent the lifelong rift while ending an impossible situation.
The parents would be prosecuted
In Texas, you can move out of your parent's house at the age of seventeen without being reported as a runaway. You do not have to have their consent, but it is still not legal. But you will not get any kind of punishment by law because of this.
A 16yo can only move with parental consent.
If the 18 year old is living in the parent's house, then they are subject to the same rules as any tenant would be according to the landlord's wishes. However, beyond that they are allowed to do as they like.
no the parent can call the cops and the child would be under house arrest if attempted a second time
Yes, a police officer can question a 10 year old without parental consent. This happens when HRS suspects a parent has committed child abuse. A parent does not have a right to abuse a child.