Giant boy feet

"I want you to jerk me off, Jason," Jacob says, pulling his boxers down some to reveal that he's already getting an erection. You feel yourself get hard at the sight of the now-giant member. You practically run along your brother's leg, pushing past the boxers to get to his cock. Although he wants you to begin jerking him off, another thought enters your mind: since you are so tiny, you could probably push yourself into his penis. Your entire body shudders at the idea of being inside of his rod, surrounded by the warm inside of it. Do you obey your giant brother, or do you defy and go inside?