Mercy King or Martha King was born circa 1638 in Massachusetts to Thomas King (1594-1676) and Anne Collins (1608-1642) and died 4 January 1668 Marlboro, Middlesex County, Massachusetts of unspecified causes. She married Joseph Rice (1638-1711) 4 May 1653 in Sudbury, Middlesex County, Massachusetts.
Siblings
| Name | Birth | Death | Joined with |
| Hannah King (1594-1697) | |||
| Peter King (1627-1704) | |||
| Mary King (1629-1714) | 22 February 1629 Shaftesbury, Dorset, England, United Kingdom | 22 May 1714 Sudbury, Middlesex County, Massachusetts, United States | Thomas Rice (1626-1681) |
| Sarah King (1634-1706) | |||
| Mercy King (1639-1659) | 1638 Massachusetts | 4 January 1668 Marlboro, Middlesex County, Massachusetts | Joseph Rice (1638-1711) |
| Thomas King (1642-1643) | |||
| Elizabeth King (-1667) | Massachusetts | Samuel Rice (1634-1685) | |