Person, I have to admit I had the same response as everyone else . . . at first. Then I remembered my friends that were married in Africa at age fourteen and the rest that were due to marry, having created excuses for post-poning the nuptuals such as an American education. Puberty is certainly the age for a renewed curiosity in all forms of covered anatomy, such as Adam and Eve reaching puberty (eating from the tree of knowledge) and noticing changes (one interpretation). In historical Muslim-African cultures thirteen would be a year later than the age of consideration. Imagine this: A boy reaches the age of twelve. His father comes to him and ask," Son, have you had an erection?" The boy answers,"No father." The father returns a year later and asks the boy again, "Have you had an erection?" The boy nods and the father begins teaching him how he must be ready to please a woman he beds. The boy will learn the jelqing
methods and advanced stretching should he and his father decide. Person, I'd say your little brother's curiosity is heathy, but the decision to teach anatomy, physiology, and body conditioning (natural PE and male health) should be discussed with consideration to the family dynamic. The very fact that you're here instead of your father makes this ackward enough. i don't know if I helped at all, but I hope I gave you something else to consider. Good Luck, and please share what you two decide.