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…

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