Python 3 solution:

def gameOfThrones(s):
    d = {}
    for i in s:
        d[i] = d.get(i, 0) + 1
    return('YES' if sum(i % 2 for i in d.values()) < 2 else 'NO')

In a palindrome, only 1 character at most can appear an odd number of times.. If more than 1 character appears an odd number times, we return 'NO',