Here is Berry's response and an interesting one it is:
From structure, first,there are two lines through the book,one is contemporary,the other is ancient. And we told about the relationship between two lines,maybe now we not see the relationship of the two main lines,but there will certain be a core point make them in series. I think the common element which connect them is water. Water,is also the essential point of title and theory.( A Long Walk to Water.) And from the title,we should notice the word---Long. it shows that protagonists met a lot of frustrations to get water.Such as Nya must spent so much time to go to the pond in order to get water for her sister,Akeer or Salva must throughout the desert to find water.
Nya's story describes that she need to pay much effort to get water which is so far away from her house to support her family. Salva's story describes that because of the war, Salva struggled to find food and water to survive along with avoiding gunmen and he never give up to find his family.
About ending,umm.... i really don't think Salva is Nya's relative because there are just 23 years discrepancy.(1985-2008) so.... i guess maybe they will meet at some point because of water ,or when Salva grow up,he will be a volunteer,to find assistance from other countries to get water，alleviate the situation of water resource of Sudan,so he meet Nya to offer help.
About evidence... because the most important element is water,so.. i think the point of connection is water.in 1985 Slava just 11 years old,in 2008,Nya is 11,too.so i don't think they are relative, i am inclined to my point as i said. furthermore，Salva meet how Sudan was short of water by himself,so i think he will be more like to be a volunteer.