Hi,
Daughter from a previous relationship ang tawag po doon.
Daughter-in-law ang tawag sa asawa ng anak mo.
Anyway, adopting the daughter of your wife from a previous relationship is done through court proceedings. There are documentary requirements and you will need a lawyer to file the petition for adoption in court.
If the biological father acknowledged the child (for example, the father signed on the birth certificate of the child), you and your wife have to obtain his written consent. There is a specific form to this, so a lawyer should assist you.
If the father did not acknowledge the child or was not named in the child's birth certificate of the child, the written consent is not needed.
If you need legal assistance, please send an email to km@kgmlegal.ph
Best regards,
Atty. Katrina