What do the siblings contribute to your group? Do their contributions out weigh the added work to constantly remind/shadow them? Are they happy, cheerful kids that otherwise play great, are they helpers?

I would consider that information in this decision. Some kids just don't get it and need the constant reminders and discipline to improve. Which is fine if they are not causing a ton of stress and negativity into the program without any positives.

Also, have you seen improvements? While they may not be at the level you want them at and believe they should be at have you seen improvement on their part (not just because you are preventing the behavior but have they shown any signs of self control in these situations? Some improvement (even little) is a positive thing and means there is room to keep improving...whereas no improvement or it getting worse could be a sign they need a different program.

It's a tough decision but there are a lot of factors to consider. One key factor is can you survive with 2 over age 2 spaces open for a period of time? Are they showing any improvement. Are they causing undue stress and harm to you and the other child that does not seem to be something you can continue with. and on and on...