How to go about reporting a child molester/pedophile which happens to be my brother?

20 years ago I was molested by my bro (I was 6 when it started) and it ended five years later at the age of 11. Throughout the years I learned to forgive him and move on with my life but now he has a 5 and 3 year old daughter. My bro's girlfriend's (not his babies' mother) daughter (ten years old) told her mom that she saw my brother touching his own 5 year old daughter down there and making her touch his ! She contacted my other brother which contacted me and asked if I believed these accusations were true...I proceeded to tell him about my own experience with our brother which he knew nothing about. Now most of the fams know about my molestation except my parents (they are vacationing out of the country). All of this mess just unfolded last night and my bro (the molester) doesn't know we know all of this! We now need a way to get them girls to safety. How do we go about this without having them do a long investigation? We need them safe NOW!!!! This is all in Florida. And also, since the girls' mother isn't much in the picture can I get at least temporary custody of my nieces? I am a single mother of two and don't make much money but I know my family will help me out. Please help!