I don't know your relatives, but I can give you a few tips about searching for them.
* Prussian/German records were kept on a very local level by a civil servant and/or the priest or minister. Therefore it's imperative that you discover their village of origin before you can go backward to these European records.
* There's a wry genealogy joke that the Prussians thought up 6 male names and 6 female names and just kept using them over and over and over. Therefore it's not unusual for a Frederich to have parents named Frederich and Fredericka and to marry a woman named Fredericka.
* In addition to the recycling of names, Prussians/Germans had up to 5 given names. One could have been their religious name, others could honor friends or relatives, and one would be the "calling" name - the name the family intended to use every day for their child. The problems arise when a person uses different aspects of their name for different occasions and/or when their priest records their names in Latin into the church records.
* Due to the naming confusions, it's always better to try to discover the siblings of the person you are searching for as a double-check that you have the right family.
To find that elusive village of origin:
* You have to exhaust the records available to you in the US. Usually, that village is named somewhere in the documents.
* Emigrants frequently carried letters of introduction from their former church. They would confirm that so-&-so had been accepted into the church and was a good church-goer. The new church would generally record details from the letter into their records and return the letter. If this document no longer exists in your family papers, then locate the church they would have joined. The church can provide the records they have for those folks and/or the records may have been microfilmed by the Church of Jesus Christ of Latter-Day Saints (Mormons) and be available for you to search at your local branch's Family History Center (consult the telephone book).
* Naturalization records frequently have the village listed. Check here to find out how to search for these records.
* Some times, if you're very-very-very lucky, the passenger manifest of the ship your relatives arrived on will give the village name (or at least an American phonetic version). Usually though, it will just say "Germany", if that, but it doesn't hurt to look.
* The same with the Federal Census records - they will usually just say "Germany", but you never know... Did Texas take state censuses? If so, definitely look for them.
Use ancestry.com's "learning Center" tab to read articles and view videos on various types of records and how to find them. You don't have to belong to ancestry to use the learning Center. About.com has a genealogy section, too. There are other sites to check, too, like the incomparable Cyndi's List.
As I said above, the PRIMARY ORIGINAL records you need, whether in the US or Germany, may have been microfilmed by the Church of Jesus Christ of Latter-Day Saints (Mormons) and be available for you to search at your local branch's Family History Center (consult your telephone book) and perhaps on their website. As always, be critical of the "MEMBER submitted" data - that can easily be in error. It's the PRIMARY ORIGINALS you should give weight to. Many records, like those of Naturalization, that are contained on the US National Archives and Records Administartion (NARA) microfilm can also be available through the LDS Family History Centers. To search for microfilms in the LDS collection, see the following link. Likewise for the NARA collections - you may have to be persistent and creative in your searches (and the films may have different catalog numbers when requested through the LDS).
------------ GermanyRoots - This is the website homepage for the above G-P-L Mailing List. It has database info and a new forum, of which many of the members are actual Germans! The site is a combination of this mailing list and several others: http://www.germanyroots.com/http://www.germanyroots.com/ , http://www.germanyroots.com/phpBB3/http://www.germanyroots.com/phpBB3/
There are many many more mailing lists and bulletin board sites like this one that may be helpful to you; explore the options thoroughly. As always, search the various mailing lists' archives for helpful discussions that occurred before you joined.
There are many German records showing up online with more constantly added. These mailing lists can help point you to them. There's lots more to know, but I couldn't type forever .^_^.Join the lists and learn from the posters.