Keep pushing. Talk with your lawyer about finding out when court dates are. Ask your sister, since she should be notified. If you know of pending court dates you might make the effort to go with your lawyer. Your sister can also sign a waiver (? not sure of the correct legal term) that allows the cw to talk with you about the caseplan.
Does the child have a lawyer, GAL, or CASA? If so do your best to contact them. I think I wasn't allowed to know if the child had a GAL/CASA, but I did call the caseworker and request that my info be given to the child's GAL/CASA or lawyer. I then contacted the county's CASA office and requested that IF there was a CASA assigned to the child that my contact information be given to them. In this way they did not have to admit knowing anything.
Contact the adoptive parent advocacy group for your area. Since you are in the same state there may be a statewide organization. This info is available at
NACAC | Parent Groups
That's all I can think of right now.
Oh, ICPC is 'interstate compact something something' and is only involved when you are dealing across state lines. It is the agreement between the two states regarding who pays supervision prior to finalization, and then adoption subsidy and covers the medical insurance for the child after placement and finalization. I don't think this applies in your case since you are in the same state as your nephew. (Did I read that correctly?)
It is also common to have to have a separate homestudy in order to adopt. Often (in many states) there are two kinds of homestudies; one for foster parents, another for adoption. If you are an adoptive family who also is willing to do foster care you would have a combo kind of homestudy. (That's what we did. It also made it easier to get legal risk adoptive placements.) Some states will allow you to have your homestudy done by a private agency. They will still want the walk through and any safety checks done, but that might be an option. However, you would have to pay for that out of pocket and only be reimbursed out of the one-time adoption expenses compensation from the state after the adoption is finalized, and you would need to save all receipts, etc. This one time payment can also cover your adoption expenses like travel, etc. The parent group for your area on the web site above should be able to give you some info about how your state works and what options you may/may not have.
Sorry, forgot to mention that we adopted a relative who was in CPS in another state. Since the child was in state custody, the parents can not make a separate adoption plan. If your relative contacts you prior to the child being removed by CPS then you would have something to work with, but once the child goes into state custody the state makes all the decisions.