The LDS websites often have good information to start with, but is not always accurate or verified - it's usually submitted by different researchers and may or may not be proven. It's a good place to look for sure, and of course not everything can be proved, but it's good to look at alot of different sites and information and see if it matches census records, church records, tax records, etc. I'm no expert at all, but much of the information that my husband has on his Tatums is from a genealogist he hired and I have tried to verify it with other records, too. Have you looked for Gary Tharp's research on Landrine Tatum and families? He has some of his work online as well. It's very possible that Nancy Rebecca Tatum had married before Orville Moses Tatum, but I just have not see it before, so it's good to check it out.