The Urantia Book speaks of Christ Michael as being a Bestowal Son, and also uses the term "bestowal" in other contexts, such as bestowal of personality and bestowal of the Thought Adjuster. As you likely know, a bestowal is a gift, or an honor given to another. There have been other divine bestowals on earth: Melchizedek was a Bestowal Son also, but he arrived as a fully grown, fully aware individual, so there was not a time when there was any question in him about what he was doing here. Adam and Eve were bestowals, but again, they arrived a adults. The only other divine Bestowal—Caligastia, who is our defaulted and deposed Planetary Prince—was also a fully formed individual upon his arrival.
There surely was a time in Jesus' earth life when he was not fully aware of his divine nature, and the fact that he himself was a Bestowal Son—a true gift to the planet. He was after all, born as a helpless infant, as we all are, and had to reach a certain maturity of mind before he could grasp the truth. But it was at age thirteen years that he began to become fully aware of all these things, and by the time he was fourteen, he was already busy formulating his mission and how he would accomplish it. So, to answer your question, I guess you could say that it is possible to be a bestowal son and not be fully aware of it. Jesus' life proves that point. But only because of the nature of the bestowal, involving the maturation of a child into an adult.
Bestowals of divine personages upon the earth are rare, and wonderful. We have been richly blessed by the bestowals given us by God, even though some of them were failures, in part or in whole. Without them, we might be worse off than we are. Surely the greatest of these bestowals was that of Christ Michael as Jesus of Nazareth. And although there may come a time when God sees fit to bestow yet another divine son upon the earth, it seems hightly unlikely that there will ever again be a bestowal like that of Jesus—born as a baby to human parents.
Thank you for this interesting question. I hope my reply has been helpful.