Some sorcerers' magical powers come from an ancestry which can be traced to merfolk, sea-dwelling humanoids with the upper bodies of humanoids and fish tails. their lineage may come from a tale of romance as a marooned sailor ancestor was nursed to health by such a creature, or they may have been born at the high tide at the apex of a cosmic event such as an eclipse.
Building off of the existing Fifth Edition rules to build a sorcerer character, the Merfolk Bloodline grants sorcerers the mysterious and charming magical abilities of the sirens.