It's entirely possible George did use that as the inspiration. He writes nuanced stuff that isn't simple good vs evil tales. His characters are all behaving as they feel they must given the situation. Unfortunately, it puts them in conflict with each other.
......which is the exact similarity with historical events around Richard III. His brother the king was married to Elizabeth Woodville, who surrounded the king with her rapacious and avaricious relatives. Once the king died, Richard had little choice but to oppose the Woodville influence, in order to secure his own hereditary rights. The parallels in the book suggest that Robert the King will soon die, his wife's rellies will try to grab the throne, Eddard will oppose them, civil war will result and the kingdom will fall to a third party from overseas.......... (is there any point in my continuing to read the book??........)
Wonderful stuff.