引用:
原帖由 garymusic 於 2009-3-16 10:17 AM 發表 
我細佬今年13歲, 因為屋企不大,
有時候我地都會一齊在同一個房間換衣服換褲出街.
最近好多次換褲時看見他在扯旗(只穿under時),
仲係激凸那種
搞到我看到時自己都扯埋一份
有一次, 我問他做咩成日扯,
他就 ...
I have found this information that able to answer your question,
this is from
www.SexEdOnline.tv :
性器官發育後，正常的男性每晚熟睡時陰莖會勃起五至六次，每次30至45分鐘。因為勃起的神經系統與膀胱及大腸的相同，在睡夢中腦高級中樞的影響大減，膀胱及直腸的神經信號可引致陰莖勃起。有時睡醒來陰莖正在勃起，十分平常，多數因為載滿尿的膀胱壓著前列腺而刺激勃起的，並不表示有綺夢。
自慰的次數因人而異，並無一定標準；不過，最重要是不應用任何物件插入孔道之中及避免過度用力，以免損害性器官。
雖然醫學證明自慰並無害處，但如果因自慰而令你產生強烈的罪惡感，或將身體的不適歸咎於自慰的行為，做成心理負擔，便最好去請教醫生或輔導員。
As my opinion, 自慰 is a private action and it's not recommend to share or do it with anyone.
But you can talk and discuss with your brother for any question.
As some members said, no need to find a special time and sit down to teach him about 自慰.
When the time has come, for example, you see him 自慰 again or only you and your brother at home.
Tell him 自慰雖正常，但切忌沉迷其中以及依賴自慰來排解壓力, 並要注意衛生。
Also, 自慰 in bathroom (toliet) or in bedroom is okay as long as keep the room clean.
Hope this help!
PS: Sorry I can't type Chinese
