Frustrated adoptive aunt

My sister-in-law's cousin had 3 children to 3 different fathers (13, 12, and 4). She has drug, and mental problems, and had her parental rights terminated for all 3. The middle child lives with bio-dad and sees bio-grandma every other weekend. 3 years ago, bio-grandma had custody of the 13 and 4 year olds. She had looked into several different options to place them with someone else because at the time, she realized that she is not and will not be in physical condition to care for them. Eventually she decided to place them with my brother and sister-in-law. They have custody of the 13 year old, and they adopted the 4 year old, and they lived with my brother's family for 2 years. Not even a year after her adoption was finalized, bio-grandma claims that she sees how stressful it is on my brother and his wife to raise their 2 biological children, and her grandchildren (the youngest has reactive attatchment disorder so she can be a lot to handle). So she decided to have the youngest stay with her "temporarily" for an "extended visit". That was December, now it is June, and she asked the ouldest grandchild to stay with her for most of the summer. Now grandma is going to con the oldest into staying with her permanantly. To make things worse, my s-i-l sends grandma a check every month (their subsidy for the youngest), and she lives in a different state! This whole situation angers me. I am their regular babysitter, so I have invested a lot of time into their lives. Both girls need therapy (oldest takes a.d.d. meds, and anti-depressants, and youngest was in therapy and occupational therapy). Now that the youngest is living with grandma, she "doesn't need those therapies". And I would be willing to bet the oldest will go off of her meds because she doesn't like them, and grandma will be more than happy to oblige to her every wish. This is so wrong! I have helped my brother and his wife correct so many bad behaviors and things that they picked up when living with grandma. And I'm so sad they are not fighting to keep their kids! I fear that the lines are being blurred because grandma is my s-i-l's aunt. I feel that none of them are thinking about what is best.for the girls' future. And I am so scared that now they will both definitely follow in their bio-mom's footsteps.