Naturalisation for step-child

Apologies if this kind of thing gets posted every week - I have been unable to find anything that answers my questions.
I need to find out what our options are with my step-daughter. I will most likely seek advice, but am hoping to find more information ahead of time.

I am a UK citizen by birth. My wife is a Japanese citizen. We have been married since 2007 (married in Japan) and living in the UK together for 8 years (since 2008). My wife lives in the UK on a FLR(spouse) visa, and has never applied for ILR due to her own uncertainty, and due to parental responsibilities making it difficult to study for the Life in UK test. She does not wish to naturalise here as it will result in Japan withdrawing her Japanese citizenship (Japan does not allow adults to be dual-national). She intends to return to Japan at some point in the future.

Our son was born in the UK in 2008 and is a UK citizen, but is also able to claim Japanese citizenship (kids are allowed to be dual-nationals under Japanese law). He is my step-daughter's half-brother.

My wife's daughter - my step-daughter - was born in 2001, in Japan, and is a Japanese citizen. She has been living in the UK on the same visa as her mother since 2008, and has been attending school the entire time. In other words, she has been in the UK most of her life.
She is currently 14 and approaching some key points in her education.
As such, it would be good for her if we could secure dual nationality for her, so that she can go to University here, and make independent choices without visa issues.

Do we have any mechanism to naturalise her now? For instance now that she has lived here most of her life, speaks natively, and is culturally British? Due to her British sibling?
Is it better to do this now, or to wait until she is 18 and can do it for herself?
Does it make any difference if I adopt her? (I've been acting as her father for nearly ten years now - her biological father is not in the picture in any way).

Thanks in advance for any links, help or advice.

She will only qualify for citizenship if her mother applies for citizenship or as an adult in her own right For both, she needs Indefinite Leave to Remain, which she can get when her mother applies for it.

For the purpose of citizenship, step parent is irrelevant and not taken into account at all.

You could adopt her, but it is an involved process and given that she will be 15 this year, might not be so easy. Where is her biological father?

CR001 wrote:She will only qualify for citizenship if her mother applies for citizenship or as an adult in her own right For both, she needs Indefinite Leave to Remain, which she can get when her mother applies for it.

For the purpose of citizenship, step parent is irrelevant and not taken into account at all.

You could adopt her, but it is an involved process and given that she will be 15 this year, might not be so easy. Where is her biological father?

+1

Stepchild can be registered as a citizen (before 18) but needs ILR plus mom to naturalise.

Edit: In my family's experience (based on cost-benefit-time analysis)...
Adoption is not necessary & won't help with citizenship.
You could consider it (or a PRA) but just for personal/family reasons.
(At 18 daughter will come of age anyway).

To gain 'Home' fees status, ILR by time a college/university course starts (on top of 3 years 'habitual residence' in UK) would be enough.

So all is not lost if wife cannot/will not naturalise.

Daughter could still naturalise in her own right, as an adult, later on.

If you are able to adopt her officially, then she will qualify for Citizenship from the date of the adoption.

Your Japanese wife wishes to retain her Japanese citizenship. Would her Japanese daughter wish to retain or lose her Japanese citizenship?

If she acquires British nationaity, your step-daughter will have to renounce either her Japanese or British citizenship at the age of 22 at the latest, as per the transcript of Japanese nationality law on the Japanese Ministry of Justice website (see Articles 11 & 14).

While I am not conversant with Japanese nationality law, it seems analogous to, though not identical with, Indian nationality law, where a child born with multiple nationalities can retain all of them till the age of majority, provided s/he does not exercise any foreign nationality (by, for instance applying for a foreign passport). Such child must elect which nationality s/he will retain at the age of majority (18 in Indian law).

By contrast, a child who is registered as a British (or any other) citizen automatically loses Indian citizenship on acquisition of another citizenship. By analogy, if your step-daughter is registered as a British citizen, it is possible that she automatically loses her Japanese citizenship, as it is a voluntary act and not something that she was born with.

So, the crux of the matter is, does she wish to be solely British or solely Japanese? She does not get the choice to be both. Neither does your son by the age of 22, as per current Japanese law.

Thanks for the quick and very helpful advice. It has certainly given us some things to look into and a better idea of the issues at hand. Thanks again.

Her biological father has not been involved in her life since long before I met them. They were never married and his name does not appear on any of her birth certificates or registration documents. I don't see any issues there.