Leonardo is the first man to manage both Milanese giants:

Leonardo as an A.C. Milan player: 1997-2001 & 2002-2003

Former AC Milan player and manager Leonardo has signed an 18 month deal with Inter Milan. The Brazilian spent four years at the San Siro with AC Milan and also spent one season with the Rossoneri as manager, leading them to third place in the 2009 - '10 season. AC Milan was the first club that Leonardo managed. Internazionale is now the second. He has signed a deal with the Serie A and European Champions until June 2012.
The 41-year-old, who assumed Italian citizenship in 2008, quit Milan with a memorable parting shot at club owner and Italian Prime Minister Silvio Berlusconi: “Narcissus doesn’t like anything that isn’t a reflection of himself,” Leonardo told La Gazzetta dello Sport.

Leonardo's A.C. Milan chairman: P.M. Silvio Berlusconi