Bob Wilks (bobwilvan @t aol.com) of Porthcawl, South Wales, writes: Ancestry shows the following marriages

1. 4th. Q. 1861 3a. 379 Rebecca Whittenbury and Henry Shadbolt.
2. 4th. Q. 1864 3a. 445 Rebecca Shadbolt and Henry Shadbolt.

Strange co-incidence or something amiss?  Rebecca's sister Mary Jane was my paternal great grandmother.  Do you have any records to throw any light on the problem without me having the expense of applying for 2 marriage certs?

You clearly did not read the Genealogy Topics page Right Name, Wrong Body? before you posted your query or you would have realised that the type of situation you describe is nothing unusual. Given names run in families (see The Inheritance of Single Christian Names) and as cousin marriages were also quite common it is very easy to make mistakes in identifying individuals - which is why the first rule of the genealogist is to check source records and not rely on indexes. The easy online access to indexes, and the failure of people to check sources, means that the number of incorrect family histories circulating on the internet is rapidly increasing - see The Dangers of Internet Genealogy.

I find it surprising that you don't mention census returns as they can be very helpful in throwing light on such cases during the 19th century. (If you are not familiar with the censuses have a look at the Tutorial.) A quick check shows a Henry Shadbolt with his wife Rebecca and family in the 1871 census and another Henry and Rebecca (with different children !!!) in the 1881 census. Clearly there were two Henry's married to two different Rebecca's - both couples being born and living in the same general area in or around Datchworth.

You should also be able to find (using Ancestry) the unmarried Rebecca "Whittenberg" with her parents in the 1851 census, but may have more difficulty in finding Rebecca "Whittenburg" on Ancestry (indexed as "Whittenbury" on findmypast) in the 1861 census as she is a servant living in Middlesex and here place of birth was incorrectly recorded as Herefordshire rather than Hertfordshire and the unreadable scrawl for the location is undoubtedly meant to be Burnham Green. The young Rebecca Shadbolt is also recorded, with her parents, in the 1861 census (but beware - there was more than one Rebecca Shadbolt listed - but the right one can be distinguished by age.)

There is another answer, SHADBOLT, Transportation to Norfolk Island, 1845. which may well relate to the same family, and you could find it useful to contact the contributors.