Those who believe in reincarnation are taught that anyone who strives to achieve union with God by living a virtuous life but fails to reach the ultimate goal will go to heaven and stay there for a long time before returning to earth. When that person is reborn it will be into a good and prosperous home where he or she will be encouraged to continue the quest for God realization.  If you practice long and hard enough you might be lucky enough to be born into a family of already enlightened parents, but that is rare and hard to obtain. That fortunate person will recall his or her former wisdom and be in an environment that will encourage even more earnest efforts than before.