User blog comment:IamJakuhoRaikoben/Chapter 366: 1000 Souls, Review./@comment-5598380-20140109213300

The 1000 souls refer to the price Natsu had to pay for hitting Franmalth right? And it increased to 2000 souls the next hit.

And i think Silver is Gray's older brother. He looks like about 30-35 years old and Gray is supposed to be 25 years old if not frozen in time at Tenrou Island.