User blog comment:IamJakuhoRaikoben/Chapter 366: 1000 Souls, Review./@comment-5598380-20140114121929

I can only think of two most possible:

1. Silver is likely Ur's husband in the past. What Natsu smelled may be the cross earrings Silver is wearing, and it's made from the same material as the pendant Gray is wearing. The necklace probably belonged to Ur and gave it to Gray. And also Silver maybe is just a code name.

2. Silver is Gray's father. Just basing from their names, it can be concluded that they are relatives.