In Metal Gear Solid 3 is snake and ocelot are brothers

No, in Metal Gear Solid 3: Snake Eater, it is never mentioned who Naked Snake's parents are; but The Boss, who is about a decade older than Snake, is his mentor, and they are implied to have been lovers. Major Ocelot, who later becomes Revolver Ocelot, is the son of The Boss and The Sorrow. Through radio conversations, Ocelot is revealed to have been born during The War while The Boss was in the battlefield. He was later abducted by The Patriots and The Boss was forced to assassinate The Sorrow to keep Ocelot alive.