Not through blood, unless they have a common ancestor. They can call each other step-brothers or step-cousins, if they like, depending on who their parents are.

That is, if your daughter Ann, who has a son Bruce, marries a man, Andy, who has a son Bernard, they are step-brothers.

If it was your other daughter, Zelda, who married Andy, then the two boys are step-cousins.

Depends on what era they lived in and what country, as that will determine the records you can research, it will also depend on what exactly you wish to find out about them......

Eg if you find a baptism record you may also find the names of their parents.
if you find them on a census record, it will tell you what occupation they had or if they were at school, where they lived on census night and who else lived in the same house ( on census night)
If you find a birth index, it may give you the mothers maiden name and also the index will give you what you need to order a copy of the birth certificate.

So when you are looking for dead ancestors, it depends on the record and what each one tells you...... that is what genealogy research is about ( which is what you have posted in unless the question is moved to another category)

Living person???? ..try FB

If it is a genuine coat of arms, it cannot be made into a trademark, because coats of arms and trademarks are covered by different legislation.

If you design a personal device, you can trademark it, which will cost you the same as any other kind of trademark. It will not be a real coat of arms or crest, however.

There's the additional difficulty that trademarks cannot be owned by more than one person, so if you want to 'hand it down' to all your children, you will run into difficulties. You don't want to end up with one of your children suing all the others for using their trademarked device.

Then I suggest you look into applying for your own adoption file, which may be as simple as asking to see it ( UK) or USA going to court to persuade a judge to unseal your file, this may give you more information about yourself as well as any other siblings you have. Even if it is not possible to see/get your file because of the restrictive practice of the country you live in, then the holders of these will often forward a letter onto siblings once they are of adult age and/or include a letter in their file should they ever wish to ask to see it.
Check out the laws in the country you live in to see what is possible and what is not