How do LDS explain the validity of their restoration of the Aaronic Priesthood?

From my understanding, LDS teach that Aaron appeared to Joseph Smith and reestablished the Aaronic priesthood. >The two divisions of priesthood in The Church of Jesus Christ of Latter-day Saints are the Aaronic and the Melchizedek. -source- The Aaronic priesthood was handed down by bloodline. >And thou shalt anoint Aaron and his sons, and consecrate them, that they may minister unto me in the priest's office. Exo 30:30 In addition, the book of Hebrews speaks of the necessity of the Aaronic priesthood as not needed any longer. Things changed. >If therefore perfection were by the Levitical priesthood, (for under it the people received the law,) what further need was there that another priest should rise after the order of Melchisedec, and not be called after the order of Aaron? For the priesthood being changed, there is made of necessity a change also of the law. Heb 7:11-12 >In that he saith, A new covenant, he hath made the first old. Now that which decayeth and waxeth old is ready to vanish away. Heb 8:13 So, given the Aaronic priesthood was handed down generationally by bloodline and has ended (vanished), how do LDS explain their Aaronic priesthood?