So, have you ever wondered why Asuka is named Langley-Soryu, when her mother was named Zeppelin-Soryu? Well, obviously because her father was named Langley - he is probably British or American, her mother half-german, half-japanese. Makes perfect sense, right? WRONG!
Asuka was born and raised in Germany - so her Parents had to live under german law. And German law is designed to make everything as unpleasing and restricted as possible.
First of all, double-last-names aren't allowed for children anymore - the law was changed shortly before the series aired, but lets ignore that for a moment, as it makes this whole thing impossible.
Secondly, there is a difference between your last name(s) and you family name. Kyoko Soryu and Friedrich Zeppelin marry. They then decide on a family name: Either Zeppelin or Soryu. This name is what their children will be called. Whichever name they choose, the person whose name is NOT chosen as family name can then decide on one of these options: Keep their old last name, adopt the chosen family name as their own, or adopt the family name while keeping their old name. If Soryu is chosen, Friedrich can thus be Friedrich Zeppelin still, Friedrich Soryu or Friedrich Zeppelin-Soryu (or Soryu-Zeppelin). Kyoko in this case has NO way to acquire the Zeppelin name - she always stays a Soryu, and Asuka will be only Soryu as well.
When you get divorced, you have a few options as well. Let's say Kyoko became Zeppelin-Soryu by marriage, then divorces the guy. She can keep her double name or revert to her maiden name. That choice is permanent, until she marries again, and makes whatever she choses her new family name. So, she can be Zeppelin-Soryu or Soryu. If she stays Zeppelin-Soryu, that becomes her new family name.
The ONLY way for both partners to adopt a double name as their family name is if one partner had a double name before the marriage already. So, if Kyoko was called Zeppelin-Soryu before her marriage to Langley, there are now four options for a family name: Zeppelin-Soryu, Zeppelin, Soryu and Langley. But no more than two names are allowed. Which means that if Zeppelin-Soryu is chosen, Langley has to give up his last name and become Zeppelin-Soryu, but all their children would be called Zeppelin-Soryu under the old law. To become Langley-Soryu, Soryu has to be chosen as family name, in wich case Kyoko would become simply Kyoko Soryu again, and all their children would only have Soryu as last name. In this case, if they get divorced, Langley has the option to return being called Langley or stick with the Zeppelin-Soryu name - he can NOT chose to keep one of the names he acquired in the marriage and add it to his own.
Pretty complicated, right? Well, it gets better. At the point of Kyoko's death, she is still called Zeppelin-Soryu, while Asuka becomes Langley-Soryu at some point. The name Langley has to come in somehow.
The easiest option is that Soryu isn't the name that Kyoko brought to the marriage, but Zeppelin is. She then married somebody named Soryu, which became their family name, while she kept her old name as well, making her Zeppelin-Soryu. That way, her husband's name just keeps being Soryu. After she died, he then marries the nurse, who is named Langley. They make that the new family name and he becomes Langley-Soryu. But remember the rules about children: They are named after the family names. So Asuka is at this point only Asuka Langley. Since she can't marry a Soryu herself to become Langley-Soryu, her father has to divorce the nurse, keep the Langley-Soryu surname, which becomes his new family name, then REMARRY the nurse and they decide on Langley-Soryu as their family name. Then, Asuka can be Asuka Langley-Soryu as well.
There is of course the problem that Kyoko definitely is not a german name, so it is highly likely that Kyoko was of (at least partial) Japanese heritage. Here the easiest option is that she was named Soryu at birth, married somebody named Zepplin, divorced him, kept the Zeppelin-Soryu name, then married Asuka's father and they kept the Zeppelin-Soryu name as family name, making him give up his old name. After her death the procedure is the same: He has to keep the Zepplin-Soryu name, marry the nurse named Langley, and when they decided that Langley is their new family name, he has the option to keep one of his old names (he can not keep both: Only two last names are allowed), becoming Langley-Soryu. He then divorces the nurse and marries her again (or any other woman) and can make Langley-Soryu the family name.
If Kyoko was named Zeppelin-Soryu at birth, her ancestors had to go through the same ordeal to give her that double-last name, if they lived in Germany. Otherwise, the procedure stays the same.
So, what does this all mean? Well, Langley can not be the birth name of Asuka's father as there is no way for him to acquire the Langley-Soryu surname while Kyoko stays Zeppelin-Soryu. That would only be possible they married, made Soryu their family name so that he can become Langley-Soryu, then they got divorced and Kyoko married somebody named Zeppelin before she died. But the series indicates that Kyoko and Asuka's father were married until her death. So his ethnicity can not be guessed from the "Langley" part of Asuka's name.
Or they just married outside of Germany. In which case, this whole post is mute.
That's why I put it in the Chit-Chat section and included the caveat that this is all pointless if german laws don't apply. Oh. And maybe I should have said "This is not meant to be taken so seriously" instead of "This is not serious." 
Sometimes I do wonder if my brain does this on purpose. 
