You are in a tough spot. You are the "presumed father" to 2 of the kids. You are not yet the legal father to any of them. Without marriage, there needs to be a court order for you to have legal rights. If you want your kids, you need to hire an attorney and file a custody petition.
Please note that my answering this question, does not, in any way, mean I represent you for this, or any other case. You need to seek that actual face-to-face advice of any attorney in your area who can further explain the law as it applies to your case.