How to say no when lending my laptop?

First of all I really don't mind lending my laptop when needed, and i can be very lenient but there are limits that i can't take anymore. I have a certain problem with my brother who seems to be asking for my laptop. Now he use to ask me every once in a while, until he will would ask me every day and if i don't lend it to him he will either use his guilt by saying strategic things like he "I'm so bored, i feel i could die" or "I guess he will have to go the cybercafe" Or demands his reasons like if i have to lend it to him. In the end i would feel guilty and lend it to him. But i hate it because it feels that my laptop is my brother's now because he uses it every day, and the during a day when he uses it about 10 hours or more a day, every day. I really don't mind that all he does is play games, the other problems are i have so little gegabytes for him to download so many games that he slows my laptop down and he does things i tell him not to do like trying to change my laptop. And when i do lend it to him i just tell him if my boyfriend message, video calls me on skype to let me know and he doesn't he just reads or hangs up on him and goes back to his games. When hours later i return with an angry boyfriend thinking i ignore him. It gets me angry because he failed on the request i tell my brother to do. I tell my parents about my problem but they don't acknowledge my problem. Sometimes i want to wake up not having to feel that I NEED TO LEND MY LAPTOP. What can i do?

Added (1). And is not like my brother has no device, he has an iphone 5s and he is there all the time. And i don't have a phone, all i have is my laptop and my kindle fire hd tablet. So i don't see the reason he has to have my laptop as a mandatory…

Be kind to your browser. Boys come and go family is forever. Let him have it and see if your parents can buy him one.

If your brother really has no need to borrow your laptop, then you don't need to feel guilty for not letting him borrow it. It is not right for him to read your messages, it is not right for him to download things without your permission as though this is something the two of you share. You actually don't need a reason to deny someone something that they have no title to other than that this is something personal and yours but you have several good reasons why he does not need to have his hands on it. Tell him no one time and put your foot down. Explain why but do not negotiate. Put a password on your computer to lock it. I'm not saying never let him use it again but he needs to learn to respect other people's property and enabling him by letting him abuse the privilege time and time again is not going to help him or you in the long run. Maybe it's time he ask the parents for a laptop of his own or maybe his behavior with yours is proof he's not ready for one yet (as far as downloading too much.) Whatever the case is, this is your laptop; this is what you're going to have to do if you want it to stay yours.

You need to set a boundary, and not change it, You no longer loan or let someone use your laptop. Set a password so they can't use it. Start eliminating his games. Copy his files to a flashdrive and give it to him. Free up space so your computer works better.

Well say yes if he can start giving you like $5 to $10 to borrow it each time. That should or may discourage him from wanting to borrow it because I believe he will not do that the first time just maybe.

Ask your parents to get him a laptop.