ZkinandBonez said:
I agree that it's a bit weird that both of these items seemingly has such an importance to the plot, but hopefully they will have an interesting explanation for Kylo Ren's interest in them.
If the spoiler site is accurate, it's a reasonable assumption that Kylo Ren is Rey's brother - making Vader his grandfather. It's not so weird that he would want Vader artifacts in that context. The saber was Vader's before it was Luke's.