Younger siblings adopted

Hi- I am 26 years old and currently have two siblings much younger than me that are recently being adopted in an open adoption, however, the state of Rhode Island is saying that biological siblings/ half siblings do not have any rights, and that visitation and relationships are based on the adopted family. I have been a huge and I mean HUGE role in my sister, who just turned 6 years old, and my brother who will be 3 is Nov. They were recently placed with a family member who did not have the time nor the patience to deal with them. There children were older and were very much involved with sports. Which I understand is very important for them, as their lives have been changed with them being in. My siblings have moved in with a first time foster family, that are unable to have children. So this is all new to them.. I guess what I am asking, is what rights do I have as being their sibling? I'm being told that they don't have anything and that's why it couldn't be written in the agreement that my mother signed during the agreement. It was said in open court, by the judge that, the foster family is interested in keeping the communicate btwn me and my siblings open. But I would like more than just there word. It has been making me wonder how many other families are in the situation that I am currently in. Why isn't there a sibling law, there is a grandparents law. Maybe creating a sibling law for all states would be something I should look in to. Thank you