My twin brother is also following this 12 year devotion. Apparently it was approved as authentic by Pope Clement XII. It was also supported by Maria Simma, who was a well known Catholic seer that reported being visited by souls in purgatory asking for prayers. Here are the promises associated with the 7-prayer 12 year novena:
The soul who prays them suffers no Purgatory.
The soul who prays them will be accepted among the Martyrs, as though he had spilled his blood for his faith.
The soul who prays them can chose three others whom Jesus will then keep in a state of grace sufficient to become holy.
No one in the four successive generations of the soul who prays them will be lost.
The soul who prays them will be made conscious of his death one month in advance.
He is 18 now, he is hoping that by the time he is 30, he will be able to use the #3 promise and choose his children to be kept in a state of grace sufficient to become holy.
He has been following the novena for almost a year now, it will be interesting to see what happens. Personally, the only trouble I have with this novena is promise #2. But thats just me.
He is also debating on whether to choose a world leader or not when the time comes.