Jeicobu
I think searching kanji for your name is one good way for studying kanji.
There are certain people who use Kanji for their name.
Half blooded people and naturalized people commonly use kanji for their name.
Nowadays many Japanese people make western-sounding names with kanji for their sons and daughters(!).

There is no kanji that is pronounced "jei", most people use mixture of "ji" and "ei" like Jay Kabira / 川平慈英(TV talent).

治 [ji/chi/osamu]administration, cure
恵 [kei/e/megumi]give/（God’ｓ）bless
護 [go/mamoru]defence/security
輔 [ho/fu/suke]help/assistance
*red letter words are Kun-yomi reading.

This kanji name sounds "ji-e-go-ho" for common Japanese but I think it is acceptable range for pronouncing as "jeikobu".

Nonetheless, I think it is unnatural to use four kanji or above for one personal name.

Minmin, you're missing the point. His name is not Japanese and therefore cannot be written in Kanji. This is why they have Katakana.

ジェコブ　（ジェコーブ） is the only correct way you can write his name.

Yeah, I know you mean. but I dont think I am missing the point.
Even katakana cannot describe accurate pronunciation. And kanji name for each person is allowed to read　in special way in certain range.
There are many Japanese whose name cannot be read by even native Japanese.

Haha. If I had to do it all over again, I'd be born in Japan with the name 鬮. Boy, wouldn't that be fun!

But katakana IS accurate pronunciation...it is accurate pronunciation in Japanese.

Foreigners using Japanese have to adapt to Japanese's rules. Not the other way around.

That is why ジェコーブ IS accurate pronunciation and is also why it cannot be written in kanji.

In fact, you could not use 鬮 for your name because of limitation called jinmeiyo kanji.

Jinmeiyō kanji - Wikipedia, the free encyclopedia

On the other hand, there is no limitation for reading kanji of individual name.

There is an increase in Japanese boys and girls who named with western pronunciation such as Mike(舞空), Kent(謙人/健斗), John(路恩). Of course I don't like this tendency, lol.

See this site.
DQN

You would find many western name given to real native Japanese, lol.

The rule you referred is NOT the real rule I think, it is just a habit.
Of course I think it is right to use katakana in business or formal situation, but we dont have to mind for private use such as screen name or nickname among our friends.

I know many friends who play Japanese Budo, and some of them use kanji for his name and stitch on their Dougi. Once I made combination of kanji for a friend who is ninja master living in Greece.

There are practices, such as sumo, which require the participant to have a Japanese name. In these cases wrestlers do adopt Japanese names, but not in the way Jacob did, but finding kanji that can make the sounds that make his name.

If you want to play with kanji, that is fine, but don't expect Japanese people to be able to read or understand what is written. That is the nature of kanji when you try to bend it to meet your own, personal needs.

So it really seems we all agree: It's technically possible to have a kanji version of your name. It just may be counterproductive unless your name is Ken (shortened version of Kenneth) and you take a name like 健.

Am I missing something here? I mean, there is a Japanese citizen from the US whose first name in English is David, and his Japanese name contains 出人 (debito, legally). At one point his legal Japanese name was registered as 菅原有道出人 (すがわら　あるどうでびと) because he married a Sugawara and they wanted their kids to have a Japanese surname. So it's legally possible and practically possible (he goes by the first name 出人 in Japan).

Yes, it is legally possible to do this, and if Jacob wants to go through the proper government channels to register his name in Japanese then I am all for it.