Maybe its because he's eviscerated countless characters in his Song of Ice and Fire series, but Game of Thrones author George RR Martin certainly knows the way to people's hearts.

A 13-year-old fan wrote to him, donating his entire pocket money of £153 to Martin's online charity campaign supporting a wolf sanctuary in New Mexico. To galvanise donations, Martin has posted a number of prizes for various levels of investment, including being a named character in his next novel – who would then be killed off. That prize was given to two people in June, including Facebook employee David Goldblatt. The young fan, who also wants to become a wolf conservationist, had also hoped to be named in the book, telling Martin "a gruesome grizzly [sic] death is all I ask for".

Martin responded to the fan, saying "those spots have already been filled by some very generous donors, and there's a limit to how many people even I can kill." But he said he was impressed with the boy's donation: "I cannot tell you how much that moved me. It pleases me no end to know that my novels, and the TV series based on them, have inspired readers as young as yourself to rally to the support of these majestic and too often stigmatised animals." He then promised to donate $10,000 in the boy's name to the UK Wolf Conservation Trust.

Martin is currently writing The Winds of Winter, the sixth book in a series that has recently won a legion of new fans after it was adapted into the hit TV show Game of Thrones. The three year period since the last novel has proved too long a wait for some readers, with some speculating that he might run out of time before completing the series – bringing an angry response from the author earlier this month.