An adult female cannot be legally adopted by her stepfather in India because Indian adoption laws, such as the Hindu Adoption and Maintenance Act, 1956 (HAMA), only permit the adoption of children under the age of 18. Adult adoption is not legally recognized under current law, making an official adoption impossible for a major individual.

Under HAMA, the person to be adopted must not have completed the age of fifteen years, unless specific custom permits it. 

While formal adoption is not possible, a stepdaughter can still seek legal recognition of her relationship with her stepfather through other legal means, such as changing her last name to his

You can be a guardian 

You cannot child above 15 years unless their is any such custom in your community 

you can approach the court for being appointed as guardian of your step daughter 

You can’t legally adopt adults under Hindu law.  Instead, treat them as step-daughters and secure their rights through a Will, gift deeds, and nominations—this gives them the same financial security as adoption.

Adoption cannot be back dated 

will takes effect on death of testator 

you cannot force them to take care of you in your old age merely be causing you are giving them property by will 

What do you mean by non practicing Hindu?

You are still a Hindu.

Even a non-practicing Hindu cannot legally adopt an adult stepdaughter in India under the current Hindu Adoption and Maintenance Act, 1956 (HAMA).

India does not have any laws that recognize adult adoption, meaning that a formal adoption of an adult is not legally possible. 

While not an adoption, the stepfather could apply to the court to be appointed as the legal guardian of his stepdaughter.

The stepdaughter may be able to formally change her last name to that of her stepfather, which can be a way to acknowledge the familial relationship legally.

You can’t legally adopt adults in India. Best option:

• Make a registered Will naming them heirs.

• Use gift deeds/asset nominations during your lifetime.

• Add a care agreement or conditional clause in Will (inheritance only if they look after you).

This gives them full security and creates a binding duty without adoption.

You are the step father of 2 step daughters 

Your  step children have no share in your self acquired or ancestral property 

Indian law does not allow formal adoption of adults (18+ years) under the Hindu Adoptions and Maintenance Act, 1956 or the Juvenile Justice Act, and a step-parent does NOT automatically become the legal parent just by marrying the biological parent. Adult adoption for inheritance or personal bonds is not legally recognized in mainstream Indian law, though rare, exceptional cases may be possible with a court’s permission under family law, but this is not standard practice and is subject to many legal restrictions.

Practical Alternatives for Adults

• Will and Nominations:
  You can execute a will clearly naming your stepdaughters as beneficiaries for any or all your assets, making their inheritance rights secure. Nominate them for bank accounts, insurance, and investments as well. However, a will cannot legally force your daughters to care for you in your old age—it only governs asset distribution after your death.

• Guardianship/Power of Attorney:
  A guardianship arrangement is not possible for adults in the absence of mental incapacity. You may, however, give them a power of attorney to manage your affairs, which only operates during your life and as per your wishes.

• Affidavit and Declarations:
  Notarized affidavits or public family declarations can record your close relationship and their use of your surname, but these do not create legal “adoption” or inheritance rights by themselves. They can strengthen your narrative socially and for administrative procedures like educational documentation.

• Contractual Arrangements:
  While you cannot bind adult children to care for you legally, you may mutually sign a family agreement for living arrangements or support. However, such contracts regarding personal care are rarely enforced by courts.

Clarification on Legal Status and Inheritance

• Your marriage to their mother does NOT legally make you their father for purposes of inheritance, maintenance, or other statutory rights, unless you lawfully adopted them as minors under applicable law—something which is not possible now as they are adults.

• Backdating adoption is NOT permitted by law, and informal arrangements cannot replicate this for legal purposes.

• Stepchildren do NOT have automatic rights to a step-parent’s property in India; only a will or gift can give them such rights.

You may proceed by making a clear will and updating nominations for all key assets. For any further drafting or planning, consult a family or estate lawyer. All advice is confidential and based on your circumstances

You are not legally adoptive father because there was no adoption taken place in the legal terms hence you are considered as step father of the children.

Besides, there is no law in India permitting to adopt an adult girl/boy.

The step children will not acquire rights over your self acquired or ancestral properties.

Special marriage act can help you.

Those forum posts are incorrect/misleading.
By marrying a woman, you become the step-father of her children, but not their legal father/adoptive parent.
Step-children do not automatically get inheritance rights in your property. They only inherit if you give through a Will, gift, or nomination.
In law, adoption of adults is barred—your secure option is estate planning, not automatic parenthood by marriage.

Adult person can not be adopted as per Indian Law.

1. Law is same for both practicing as well as non-practicing Hindus.

2. As per law you can not adopt any adult person.

You can not be the adoptive father of any adult person even if you marry her mother.

1. In case of Adoption of child or children by step-parent, the biological and step parents have to register on the Designated Portal of CARA and provide relevant documents by uploading the same online through the Designated Portal.
2. Submit an application under SCHEDULE XXV [regulations 54(6) and 55(5) of Adoption Regulations 2022]
3. You need to apply in SCHEDULE XXXII for adoption to District Magistrate.
4. All the above procedure is secular applicable to all religions.
5. What is the opinion of others on this website is not my concern, what i gave you is as per the latest regulations framed under Juvenile Justice Act that governs all adoptions in india. 

You are right that under the Hindu Adoption and Maintenance Act, 1956, adoption of a person above 18 years of age is not legally permissible. Since your wife’s daughters are already majors, adoption is ruled out. However, there are other legally recognised routes through which you can establish a relationship or secure their status similar to that of your own children:

1. Stepchildren status – Under personal laws, once you marry their mother, the girls are considered your stepdaughters. While this does not automatically confer inheritance rights from you, you may voluntarily give them rights.

2. Nomination & Will – You can execute a Will in their favour, ensuring they inherit your assets. You may also nominate them in financial instruments, property, and insurance policies.

3. Guardianship/Dependents – Though adult guardianship is limited, you may execute documents recognising them as your dependents, which can strengthen their rights in certain circumstances.

4. Settlement/Trust – Creating a family settlement or private trust in their favour gives them long-term security akin to adoption benefits.

In short, while adoption is not possible, through testamentary instruments (Will), nominations, and settlement deeds, you can legally secure their financial and familial status.

- Under the Hindu Adoption and Maintenance Act (HAMA), adoption only allows for the of minors i.e. below the age of 18.

- Since, your wife’s daughters are 18+, you can’t formally adopt them through HAMA

- Further, even under the Guardianship Act, a major cannot be adopted , and only some special circumstances this can be granted. 

• You cannot adopt adult step-daughters; “back-dating” is not legally recognised.

• Marriage does not make you their father as per law.

• Best way: secure their rights through Will, nomination, gift deeds, settlement deed, and if you want care in return, use a maintenance agreement.

• This way you get all practical benefits of adoption, without breaking the law.

for more details you can take my consultation

regards,

Adv. Arunkumar Khedia

(Bombay High Court)