I have seen some theories that Val and Jon Snow are sister and brother. It's a variation on the idea of a twin birth at Tower of Joy. Under this theory Mance Rayder is Rhaegar Targaryen, Dalla is Lyanna and Val and Jon are their children. I was thinking about this when I thought of Jean Valjean - the principal character in Les Miserables. Les Miserables also has characters who are brother and sister without being aware of it. http://lesmiserables.wikia.com/wiki/Gavroche_Thénardier A great question to ask George RR Martin is whether he thinks that Les Miserables has influenced A Song of Ice and Fire in any way.