If you are an adoptive family (or are at least considering adoption), let me encourage you to read the book of Ephesians with your own adoptive family in mind. It is full of instruction that will strengthen and enrich relationships within adoptive families (or in any family for that matter). Jeanne Stevenson-Moessner, author of The Spirit of Adoption: At Home in God's Family, writes:
“Shortly before he died, the New Testament scholar Bo Reicke was reworking his approach to Ephesians…In his revision, Reicke was going to assert that the last three [chapters of Ephesians], filled with practical application, were the heart of the book. Chapters 4-6 are filled with advice and admonitions about how to live and love as family of faith: Children of disobedience and wrath are to walk as children of light. Specific instructions are given as to how ‘beloved children’ related to one another. Household codes (rules of conduct) are offered in chapters 5 and 6.
“Why are these practical chapters the heart of the book? Because they reveal how to live as adopted children of God. Ephesians 4-6 develops the doctrine of adoption that is presented in the first three chapters. They not only talk about how to live as Christians; they tell us how an adopted family functions. For example, Ephesians 4:11-13 develops the theme of acceptance-of-differences, which is an essential theme in healthy adoptive families; the passage elaborates on this theme by advocating an acceptance-of-differences- of-gifts given by Christ for ministry. To illustrate this theme, in Ephesians 4:15-16 an image is developed of the various parts of the body. The body comprises different limbs, organs, and systems, but it is the very difference that makes the body truly functional. Ephesians 5:1 contains an exhortation to be as ‘beloved children’ as Christians in Ephesus. This injunction was not given to flesh-and-blood siblings, but rather to the diversified followers of Christ who were forming a family by faith” (Jeanne Stevenson-Moessner, The Spirit of Adoption: At Home in God’s Family, 98-99).
You don't have to read too far into Ephesians to recognize that it is a letter that cares deeply about theological adoption. Just four verses in Paul writes, "In love [God the Father] predestined us for adoption through Jesus Christ, according to the purpose of His will, to the praise of His glorious grace." Paul chooses to introduce this great epistle by highlighting God's gracious work of adoption through His Son. No other book in the New Testament does this (though the Gospel of John comes close—see John 1:12).
I think Bo Reicke was right when he argued that the purpose of Ephesians 4-6 is to instruct Christians about how to live within God's adoptive family. If you are adoptive parents that are looking for a book that will provide much wisdom for your adoptive family, start with Paul's letter to the Ephesians. Not only is it time-tested; it's also inspired by the One who not only knows everything there is to know about adoption but also invented it, God.