Thank you for your enquiry. Please provide some clarity to your question. Your children were born "here" Where is here? Assuming you mean the UK, children born in the UK after 1 Jan 1983 are not automatically entitled to British citizenship. Could you provide more information on what basis your children were granted British citizenship in the first place and what was the reason given for the revocation. A revocation is usually made without a reason.
A child who is not already British becomes British from the date of the adoption order if in the case of joint adoption one of the adopters is a British citizen on the date of the adoption. But if your children were already British then they remain British.
The plain fact that a person born in the UK after 1/1/1983 and at the time of birth his father or mother is a British citizen that person acquires British citizenship by operation of law. Do you have evidence of the fact that at the time of birth their natural mother or father is a British citizen? because if you do there is a case to answer in my opinion.
My name is ***** ***** I have been a solicitor for more than 36 years.
The problem is that when a child is adopted in accordance with UK law, the child generally acquires all the rights and entitlements of a biological child.
In legal terms it is as if the adopted child was born to their adoptive parent or parents.
So just as a child who is legally adopted by British citizens will (usually) be treated as a British citizen regardless of the country of its birth, in your case your children hold dual Australian/Spanish nationality and can chose which passport they apply for (or indeed apply for both)
However since they have lived in the UK for more than 10 years they can apply to Register as a British citizen - details here
My name is ***** ***** I practice and specialise in British Immigration Law and have done so for years. I am a Chartered LE Immigration Lawyer England & Wales and a non-practising Barrister.
Section 67 of the Adoption and Children Act 2002 does not apply for the purposes of any provision of the British Nationality Act 1981 or any other provision which determines British citizenship, British overseas territories citizenship, the status of a British National (Overseas) or British Overseas citizenship.
You cannot register to be a British citizen if you are already automatically British by operation of British Nationality law.