Seeking honest advice!

My husband and I have been foster parents for about a year. We’re both 25, have no bio kids (yet), and we have great support in family/friends/church. We’ve been fostering a little girl (1.5 years old) since October 2020, and it’s now clear that parental rights will be terminated. We’d absolutely love to adopt her, she’s an incredible little person and we feel we’re a perfect fit for each other. Everyone who’s part of the case says she’s thriving in our home, and we’re thriving too. Our little one has 4 older brothers ages 6, 8, 10, and 15, who live in an excellent (like way, way nicer than our house) group home. They’re happy there and have so many resources and good relationships. The oldest has made it clear that he wants to stay there and not be adopted, and the younger brothers look up to him, but aren’t old enough to make that call according to CPS. CPS has asked if we’d be willing to adopt the 6, 8, and 10 year old along with their sister. If we say no, they’ll advertise all 5 children as a group to be adopted together, and we’re afraid of the risk of losing her, or of her losing all her siblings if they move away. We’ve done lots of hard things for 25 year olds but the thought of 4 kids up to age 10 is so overwhelming! Financially and emotionally, we think we could make it work, but we truly don’t know what’s best for the kids. The siblings have a good relationship and we do extra visits, birthday parties, and events with the brothers, but they’re not exceptionally close with their 1 year old sister. What experience do you guys have with adopting a sibling group of 4, or separating the group? How did you decide which of those was best for the kids? We’ve been praying about it a lot, but don’t feel peace with either answer yet.