Are you referring to this Robert Murrell? If so, he was the son of an earlier Robert Murrell and wife Sarah. After the first Robert's death, Sarah remarried an unidentified Mr Hooker and left later records as Sarah Hooker. There are indications that Robert Murrell and Sarah probably came from the Salem, Mass. area as part of the Wappetaw group.

Abstracts of Wills of the State of SC - Caroline T Moore
Volume 3
(p20)
Will Book QQ 1760-1767
Robert Murriell, Christ Church Parish, Berkeley County. Wife: Susanah, liberty to live in house on plantation where I now live during her widowhood. Sons: Robert, plantation at head of Sampit [River]; John, plantation at Washo in "Santee Parish"; Paul, land in St Dennis' Parish where John Combe now lives, land at Winyah; Peter, land where I now live. Daus: Mary Bell's husband "her share already;" Martha, Susannah, Elizabeth, Damaris, Sarah. Exors: wife; Mr Richard Weathers, Capt John Dutarque; son Robert if any of the two men do not qualify. Wit: John Cuming, Vallintine Darr, John Baskerfield. D 7 Apr 1759, P 22 Jan 1762, R nd p136

John Morrall (of the Murrell's Inlet land) was the son of John Murrell and wife Elizabeth. John Morrall and his brother William Morrall were closely associated with the Robert Lewis family originally from Barbados. It is possible but not yet proven that their parents John Morrell and Elizabeth might also have come from Barbados.

There was no close contact between the early John Murrell/Elizabeth family and the early Robert Murrell/Sarah family or their descendants. If there was any kinship between these families, it was probably very distant.

For some of the records concerning these families, see
http://freepages.genealogy.rootsweb.com/~fcharper/MaryMurrel...
http://freepages.genealogy.rootsweb.com/~fcharper/JohnMurrel...