My ancestor Phillip Post came to Australia from Eltville near Frankfurt in about 1860.
He had a son Conrad from whom I know I descend.
How would I discover the descendants of Phillip Post who served in World War 2?
Genealogy & Family History Stack Exchange is a question and answer site for expert genealogists and people interested in genealogy or family history. It only takes a minute to sign up.Sign up to join this community
Note: this answer pertains to the question as it was originally asked, and not necessarily to its edited form. The question was how to find any surviving relatives of Phillip Post (who came from Eltville near Frankfurt around 1860) who might have served in WWII.
The usual recommendation for studying your family history is to start with yourself and to work backwards from there, taking small steps at a time. Your goal is to find information about the people in your family, and -- once you get past the point where you know your own relatives because they were alive at the same time you -- to be able to have some confidence that you are looking at the right people, and not someone else who happens to have the same name.
Working forwards in time, to find all the people related to someone in the past, is sometimes called "reverse genealogy" because you are moving in the opposite direction in time from the researchers who start with themselves, and want to find out who they go back to. The more formal name of the process where you look for all the descendants of a particular person is Descendancy Research.
All of the techniques that you can use to do genealogy research which goes "back to" someone are also applicable to descendancy research. Document and evaluate all the sources that you find. Work forward in small steps instead of making huge leaps.
The crucial difference in doing descendancy research is that you need to keep track of all the people you find that are descended from your chosen ancestor, instead of concentrating on your own direct line. Focus on a single family group at a time and collect material about sibling groups. In the course of doing that, you will find information about the children of each set of siblings, which will give you the links forward to the next generation. You will also have more confidence that you have correctly identified the parents of each sibling group if you study an entire group.
Another way to be sure you have the right person is to study their friends, associates, and neighbors as well as the family, which is sometimes called a "cluster" or a "FAN Club". See QuickLesson 11: Identity Problems & the FAN Principle by Elizabeth Shown Mills for how to find clues by looking at groups of people. This process is especially valuable for descendancy research because it encourages researchers to study people in groups. Looking at the community around the family may give you clues to siblings and relatives that you might have missed if you were concentrating only on a single line.
I'll emphasize again that you want to have confidence that you are looking at the correct family, because when you do descendancy research, you will be collecting information about a LOT of people. If you get two people with the same name mixed up, you will collect a lot of information about people named Post who served in WWII but they may not be related to you.
A basic outline for doing descendancy research for Phillip Post might be:
You asked specifically about your relatives named Post who might have served, but I encourage you to study the daughters in each generation as well as the sons. Married daughters can provide important clues that you have records about the right family, because you have their husband's surnames to study, too. It makes it easier to find out if you have the right Conrad Post in a particular generation if he has a brother-in-law -- you aren't just looking for "Post" but the combination of those two surnames.
It is not necessary to have a computer program to keep track of all your research. People studied family history for a long time before we had computers. But if you want to use a lineage-linked program and need help choosing something, check other questions here or do a Google search for "genealogy software reviews". Some of the popular commercial programs have free versions that you can try out before purchase. However, it is also possible to use other software not intended for family history, such as Evernote, a word-processing program, a spreadsheet, or whatever other note-taking software you feel comfortable with. A paper journal or a blog works too -- just do something to keep track of what you have found, and what research questions you want to address next.
For family history, and especially descendancy research, I recommend making use of historical newspapers whenever they are available. Obituaries are particularly useful for descendancy research because they can have extensive lists of survivors of the deceased. The amount of material in a well-written obituary is far more extensive than a census record, and can often give you a much larger picture of the family structure than a census does. It can be much easier to start with an obituary and then use it to find historical records about that person than it is to go the opposite way. Since the obituary is written at the end of a person's life, it gives you a more complete biographical picture of the person than any historical record, which is a snapshot taken at a single point in time. However, it is still important to find the historical records about each person in order to learn more, and to verify what the obituary says.
As a part of my research, I regularly collect all the obituaries I can, and analyze the obituaries of a sibling group as a group, establishing both the birth order and death order of all the siblings. If you don't know the death date of one of the siblings, you can narrow the window for their date of death by seeing whether they are listed as a survivor in another sibling's obituary.
Another important difference between doing "go back to" research and your question is that you are looking for living relatives. Contacting living relatives is not on-topic for this area. See the FAQ: What Topics Can I Ask About Here?:
Please note: You must not include here in any circumstances information (including name, date and place of birth or any other details) that would allow identification of any living (or possibly) living individual by somebody reading this site. In practice, this means details about anyone born in the last 100 years, whether they are believed to be deceased or not, and whether or not they have given their permission.
The how-to videos in the resources list talk about how to find living relatives and ways to contact them.
Many of the resources I linked to below are USA-centric. If you are doing research outside of the USA, look for historical records and newspapers for the country you need, and use the search tips in these videos and handouts on those sites.
For instance: Ancestry's guide to research in military records (link below) says:
Check birth years. Draft ages during World War II extended from ages 18 to 45. Search for people born between approximately 1897 and 1926 (give or take a few years) in both draft cards and enlistment records.
Different countries may have had different requirements for service, but the principle of checking the birth date range to find possible veterans of wars will apply for any country.
As you work through this process, you will probably discover all sorts of specific questions about how to find records about Philip Post's descendants. Please come back and search for other questions that may be similar to your problem, and if those questions don't help, post those items as new, separate questions.