The crematorium will normally arrange to release the ashes either to the undertaker to pass on to the person who paid for the funeral, or will arrange for the ashes to be sprinkled in the Memorial Garden at the crematorium. Talk to your step dad about this. If he has the ashes, and wants to do something with them about which you are unhappy, ask him if he will let you have a small quantity of them so that you can sprinkle them where you wish. There's no rule that says ashes have to be sprinkled in one place, or by one person.