Hi again,
Searched the Brecon 1851 census, nothing on there, searched
<
http://www.familysearch.org>www.familysearch.org for a marriage they are
not there either, looks like you will have to keep searching, like us all
eh!! If you have dates at all or where they were born would help a lot.
Have you tried the immigration web page upon landing in the USA ?
cheers
Rose