I’ve two (rather strange!) questions. I hope you'll answer them.
1. Have there been saints and avatars in other planets in this universe?
2. I consider Yogananda as my Guru, and I desire very much that he would still be in my next life, even if I would be born in another planet. But I strongly remember Swamiji saying that we would get a Guru only of Master’s line if that is the one we worship, in any life. How is it then that one of these Gurus would be my Guru in another planet?
From what Paramhansa Yogananda said, it seems fairly certain that saints and avatars are abiding on other planets.
As for your second question – the most important point is to deepen your attunement with Yogananda and feel his presence through the practice of the techniques that he taught (the Energization Exercises, Hong Sau, AUM, and Kriya). Let your heart open with ever deepening devotion to God and Guru and then He will take care of you, whether you are born on this planet again or on some other planet. Remember that an avatar such as Yogananda isn’t limited by time and space so there’s no need to have any concern in this regard.
In divine friendship,