Someone keeps spreading poo on my car?

Take photographic evidence of it. Also, aren't the cops and animal control there conducting DNA analysis for dog poo offenders?

At any rate if it were me I would put 2 and 2 together and realize who was responsible, you seemed to have that figured out anyway, and return the poo to your stepdad's brother's family. In fact I would launch the bag of poo and watch it impact on their front door and windows. And if that didn't stop them I would target them personally.

When you said spreading poo I imagined someone with a butter knife getting a nice even coat.

Poo in a bag is a different kettle of fish. But still stinks.

Catch whoever it is in the act, then threaten to report them to the police for harrassment. That should stop them.

If it does turn out to be your relatives, perhaps you, your mum, stepdad and brother could all go round to their house and each curl one off on their windscreen.

I reckon they (Your step lot) should be kept on a leash.

Have the poo DNA tested and get them bang to rights, lock then up in the local vets pound for two cans of Butchers and a Bonio or (three months and two days whichever is your preference).

At least it's not margarine being left on the windscreen that makes an awful mess. Ignore it they will get fed up in the end.

Have a bat n stay upp all nite till 7 am. Be ready to catchem . Round house that ***** beat till he lerns shr lerns a lesson

Spy on them to see who is putting it on his car! Have a neighborhood watch.

Then catch him in the act, or report to the police. Any type of damage to a car CAN be reported to the police, go up to the police station and let them know

I'd suggest putting a camera (night vision) watching the car and see who's doing it. Then you can have evidence to take to the police and have them arrested for vandalism.

I'd go ahead and report the incidences to the police now as well, so you have documentation of when it has happened.

Sounds like a bunch of sheet to me.

Really, we know who it is now, call the police and report whom you believe is the culprit.

Set up a camera and turn it in to the cops! Or just someone stay on guard when they show up taser them and call the cops

Someone with a personal issue with your family is doing it. Park in front of their house and they won't do it.