The Brazil international playmaker is out of contract at the end of the season and is free to talk to other clubs in January.
“Anything is possible in football, but if I have to be honest, my brother has a contract with Milan until 2011 and there is time to talk,” De Assis told Sky Italia.
“We have respect for the club. We are organising things gradually, waiting for the right moment to renew with a great deal of calm.
“Ronaldinho wants to be concentrated on playing. Right now Milan have to win and my brother must only think about these important games.”