I'm trying again on this thread because I feel quite strongly about it and the poor child caught up in this.
"Then both her and her hubby said when they were going through the process they rejected three children before her. I said why the answer was we can't cope with a child that as medical problems i to this day im digusted by this so before im judged i wasn't the one adopting a child based on health."
This sentence alone tells me very clearly that you have no idea what you are talking about when it comes to adopting children and therefore I really think that other than providing your sister with support to address her drinking and encouraging her to ask for help for the adoption team at her local authority, I think you should steer well clear of getting involved.
Anyone who is "disgusted" by adoptive parents turning down a match on the basis that they cannot cope with the problems a child is already presenting with is so far from understanding the issues that any "help" you provide is unlikely to be well-informed, however well intentioned.
Your sister needs to be encouraged to address her drinking and jointly they may need help with the parenting their child needs.
My initial view based on what you've said so far is that you are the last person they need to get involved.
If your sisters family are causing your children significant problems (like violence) then you need to stay away for the time being or see your sister without the children there.