On the GEN-MEDIEVAL-L mainling list Todd Farmerie said on Sep 29, 2012 - "The problem is that El Cid was a member of the obscure local nobility, and all we have as evidence for his parentage are the already myth-tainted celebrations of his life compiled as epics. If you trust the pedigree given there, then you can match up the names with an established family of the high nobility. However, many authors consider this material to be hopelessly tainted by a desire to glorify the hero. Given that surname usage had not developed yet, it is a matter of faith in many cases to conclude that a given person in a document is the person of that name in the legendary pedigree. Simply put, there is no getting around this. As to Jimena, what we know is that she had brothers who were counts and had the patronymic Diaz. She is reported to have been a kinswoman of Alfonso VI, and this has figured heavily in older attempts to provide her with a pedigree have foundered on this rock that likewise derives only from the epic material. A lot of ingenuity has been put into compiling an ancestry for her, but with her mother it comes down to accepting the authenticity of a charter which has been doubted, and with her father, a process of elimination based on geography, onomastics, some assumptions about (or dubious records referring to) social status. The short answer is that there are theories out there, but consensus is wanting because of the lack of quality source material and different perspectives on the value of that which we do have."