That's a good piece of information Jeremyg. A highly attained pratitioner like Tulku Drakpa Gyeltsen could have multiple emanations which can function on their own, so it is not impossible that Nagri Rinpoche (assuming he really is an emanation of Tulku Drakpa Gyeltsen ) and Dorje Shugden exist at them same time, and I am sure these two are not the only emanations of Tulku Drakpa Gyeltsen. Samdhong Rinpoche is also said to be an emanation of Dorje Shugden. So let's see what we have here...Tulku Drakpa Gyeltsen emanates as Dorje Shugden, Dorje Shugden emanates as Samdhong Rinpoche, and Tulku Drakpa Gyeltsen also emanates as Ngari Rinpoche....the possibilities are endless...
Tulku Drakpa Gyeltsen and the 5th Dalai Lama were very close back then, both stayed in Drepung Monastery, one in Zimkhang Gangma, the other one in Zimkhang Oma. So it is not surprising that they decided to become brothers in this life!
Everything is just a play, a show performed by the enlightened minds for the unenlightened, so once we realize this, all the more we should get back to our practise and don't waste time indulging in the "play", we should have surpassed that already, leave the "play" to those who still need it...