How do I stop talking to a creepy guy on Facebook?

[sweetlittlebumblebee]

I've known the guy since I was little. He visits my neighbor (his mother-in-law) with his wife and kids every summer. He is nice enough, but it is weird to be constantly messaged on Facebook by a middle aged man while you are still in high school.

I don't want to be rude and tell him to stop talking to me, and he would notice if I blocked him. I also have made the mistake of giving him my cell phone number... Why did I do that...? -.-

This Christmas he gave me a lowcut spaghetti nightgown and a cami... He then asked for pictures of me wearing them. I ignored that comment and never sent a single picture of myself.

He sends me "funny" cat pictures and people of Walmart pictures. Some of the pictures he sends are inappropriate, for example 3 alpaca's humping and a dog off to the side; with this picture he said "Poor dog, missing out on all the fun." Even though this is harmless, it is totally inappropriate to make dirty jokes and go out of your way to send them to a teenage girl over Facebook.

I send back a few funny pictures just to be nice, but honestly, I don't want to be bothered with it anymore.

He refers to me as his little sister... He might just be lonely and doesn't know how to interact with people my age.

I never really have been into Facebook, infact I don't even talk to my friends in real life on it anymore. I don't want to have to respond to him every time I log on.

How do I nicely ask him to stop messaging me?