how do i turn off icloud sharing of my messages, and contacts with all devices on my account? I just want it to save each one individually

i was on an account with itunes and icloud with my brother, but i got a new phone and a created a new ID for both. today my brother was getting copies of all my text on his iphone, and it then synced both our contacts to each others phone. Next me and my fiance share the new ID created and also today all the contacts that synced from my brothers phone to my phone then were merged with my fiances contacts!!! What is happening and how do we each create our own privacy without merging contacts, etc and still use the icloud backup feature?