Yes. The grapefruit is a hybrid of the larger pummelo (Citrus grandis), and the sweet orange (Citrus sinensis). The first cultivated grapefruits met with a mild response due to their acidic flavor and astringent pulp. The modern, sweeter, less acidic grapefruits are the result of naturally occurring bud sports that had different characteristics than the original tree upon which they were discovered. The branches that produced the better tasting fruits were grafted to other rootstock to cultivate these superior varieties.