We are disrupting our placement

Without a doubt these children need to be in a home where they are the only children, and we were the third placement for them and the previous ones stressed this (now we find out!!!) so they did find someone to take them who doesn't have any kids as hers are all grown (she is a grandma and she has taken the twins for respite before, so they do know her). I'm very frustrated that we are just finding out now that the pastfoster parents also said the twins really need to be in a home with no other kids:(