All the relationships appear "Sibion" family related.
Thomas is the son of William Sibion and Elizabeth(Lancs OPC)
Mary Williams is nee Whitefoot,nee Sib(b)ion.Daughter Rebecca from first marriage is with Peter and Mary in 1841.
Thomas Edwards is the illegitimate son of Margaret Sibion,presumably a sister, and Thomas Edwards.
Margaret Sibion then marries a John Hughes(1833),and the John of interest is their son.
I can't find this family on the 1841,perhaps one or both parents have died.There is a John Hughes of the right age in the St Asaph workhouse in 1841,but the name is obviously not uncommon.
Regards
Roger