Dear Prideful muslim,
I assume from your post that you CAUGHT him spying or FOUND OUT that he was spying, rather than he came up front and said he is observing or monitoring your facebook page, considering that you said he "knows what I have in it" so obviously he didn't just tell you up front.
So it is spying.
Two companions were once out monitoring the streets and checking on any events for the prophet (neighborhood watch, at the time called AAasAAasa عسعسة) and passed next to a home that they heard laughter coming out of it and music, and stood there to distinctly hear that it was "drunk" laughter. They realized the homeowner was drinking. One looked at the other and said "God and his prophet are being disobeyed here tonight" and the other said "Yes, for God and the prophet told us not to spy on each other. Let's go." And they left. The prophet ratified their actions, for to interfere their sin had to be public.
So you see even though they were charged with keeping the peace and monitoring, they could not spy on the closed house, because that is PRIVATE, not public. God says in the Holy Quran: "[FONT=Verdana,Arial]O you who have attained to faith! Avoid most guesswork [about one another] for, behold, some of [such] guesswork is [in itself] a sin; and do not spy upon one another, and neither allow your*selves to speak ill of one another behind your backs. Would any of you like to eat the flesh of his dead brother? Nay, you would loathe it! And be conscious of God. Verily, God is an accep*tor of repentance, a dispenser of grace!"
If your facebook page was public, then he wasn't spying, and just looking. If you made it private to only your chosen friends and he used a program to access it or convinced someone to break into it or to simply look through from someone else's account and maintained it, then he is spying and is commiting a sin and you have a grievance against him.
Second even if he is monitring for bad influence, then he was to monitor his own son (whether or not he is below 18, this 18 minor/adult issue is unrelated to Islam) after telling him clearly that he is monitoring him. If he argues that his son wouldn't like it or agree, then he has answered himself as to how deplorable it is to be monitoring someone with their knowledge, imagine how deplorable it is to do it behind their back.
Additionally without regards to your age, your cousin has no supervisory rights over you just as you don't over him, as a matter of fact you have every right to bring this to the attention of his parents if they are alive, or another family elder because this is a transgression and a sin that he needs to repent from and apologize for, especially that you are a woman and he is a non-mahram man.
And may God maintain our guidance on the path
[/FONT]
brother,
Sorry about that. I just assumed it because of the whole "bad influence" idea. I couldn't wrap around the concept of two boys from the same family and then one thinks ill of another's values and morals and tries to investigate directly without going through the parents. I thought you were a girl since that would have been the only logical thing, as a girl's normal behaviour might still put ideas in his son's underdeveloped mind (boy-girl relationship wise) and that he wanted you two to remember that you're relatives but non-mahram.