I need help fast. My sister is losing her kids, im getting custody?

My sister and her boyfriend got into a fight, cops were called and now they are charging her and her boyfriend with Felonies, his for Felony Battery & hers for felony child endangerment. This is not the first time she has lost her kids, the last time they also stayed with me, but she got them back. Now the cops are going to give them to me again and she has agreed to sign over custody. But what do I do now? How can I raise her 3 and my 2 in a way that's good for them all? Also, this just happened so I don't understand if it is permanent this time. Any suggestions to help? Thank you.