If you are referring to the Warner Brothers cartoon cat Sylvester (nemesis to Tweety Bird), probably not.
If you are referring to the singer Sylvester who recorded late 70's chart topping disco hits like "You Make Me Feel (Mighty Real)" and "Dance (Disco Heat)" - featuring back up singers Two Tons O' Fun (later The Weather Girls of "It's Raining Men" fame) - then yes, absolutely without a doubt he was gay.
He was a staple of the dance club scene in San Francisco and politically active, supporting Supervisor Harvey Milk and helping to fight against AIDS/HIV or GRID (Gay-Related Immune Deficiency) as it was known at the time.
Chris Colfer who plays Kurt Hummel and Jane lynch who plays Sue Sylvester are both gay
Harley Sylvester goes by Sylvester.
Sylvester Stallone's full name is Michael Sylvester Gardenzio Stallone.
Rocky Balboa is a fictional boxer played by Sylvester Stallone in the various "Rocky" films. There can be no 'real' drawing as he does not exist.
Chris Colfer(kurt) Jane Lynch(sue sylvester) Jonathan Groff(jesse st. james) and the creator Ryan Murphy
Sylvester Calzone is an actor in the OddParents world, who is an obvious parody of Sylvester Stallone.
Albert Sylvester's birth name is Albert James Sylvester.
Joey Sylvester's birth name is Joseph John Sylvester.
Jules Sylvester's birth name is Julian Richard Sylvester.
Leif Sylvester's birth name is Petersen, Leif Sylvester.
Nick Sylvester's birth name is Nick Carter Sylvester.
Sherri Sylvester's birth name is Sherri Kay Sylvester.