Mom wants to give me money, but what if Dad won't let me?

If you are a minor, it is illegal for your stepfather not to let your mother give you money. You can apply for legal arbitration. Before that, you can tell your stepfather that everyone will agree not to mention the law. If you are an adult, your stepfather has no right to interfere with your mother. You can also talk to your stepfather. If it is not appropriate, you can apply for legal aid.