I think you offer some good points here, but even though the NT does use this language and admittedly it is broader than the focus on the family meaning often ascribed to it, I still think that we may run into problems incorporating that same language into modern contexts.

Our langage on this issue runs into issues with cultural engagement. As our society becomes more post-Christian, the transference of meaning continues to decline. At the same time, if we are going to continue to use this language it is going to be counter-cultural. That may not be bad, since the early church was often accused of incest due to their own calling each other brothers and sisters. At the same time, it is going to turn a lot of people off and may cloud the message.

In short, I think you are correct that kinship language is narrowly defined in many Christian subcultures and is therefore difficult. At the same time, I also think that simply because the NT uses kinship terminology more broadly than contemporary Christianity this fact doesn’t necessarily mean we should adopt that same language given some of the difficulties that may come with it.

I am just thinking through this, and would love to hear your thoughts as well.

First, siblings sometimes can be the furthest thing from a friend. I have amazing friends. Individuals who I have lived tear-stained moments with but who endure, comfort, and mourn as well. At the same time, I know people whose siblings wouldn’t come close to these intimate relationships.

Second, I think we are quick to call someone a friend, and the term has lost much of its significance. That doesn’t mean I am on some rally to restore the term “friend” while simultaneously bucking the lexical trend. Nevertheless, the term lacks significance in a facebook friend generation.

Our first president commented on friendship, and his words have been a constant reminder to me of whom I allow to enter the intimate world of friendship in my own life. He stated, “Be courteous to all, but intimate with few, and let those few be well tried before you give them your confidence. True friendship is a plant of slow growth, and must undergo and withstand the shocks of adversity before it is entitled to the appellation.”

So, yes I agree that there is a form of friendship that is qualitatively distinct from the all to unfortunately common experience of most. However, I don’t think we can rename it entirely. Every title, be it father, mother, sibling, and friend has new creation examples, and each of those titles also have experiences of fallen expectations and experiences. Thus, I don’t think sibling or a different title is the answer.

What do we call this degree of intimacy that is so palpable but our langage fails to describe? I am not sure.

Just some thoughts on this issue that I thought I would share. Hope your research is going well.

I would also mention that just as we need to resist inadequate understanding of friendship, we also need to resist an inadequate understanding of familial relationships. In the New Testament context, “family” did not refer just to the nuclear family. Even Greek words like ἀδελφὸς, which we usually translate “brother” actually had a rather broader meaning, and could refer to other male relatives.

For example, the Septuagint gives Genesis 14:16 as: καὶ ἀπέστρεψεν πᾶσαν τὴν ἵππον Σοδομων καὶ Λωτ τὸν ἀδελφὸν αὐτοῦ ἀπέστρεψεν καὶ τὰ ὑπάρχοντα αὐτοῦ καὶ τὰς γυναῖκας καὶ τὸν λαόν. The NIV translates this “He [Abraham] recovered all the goods and brought back his relative [ἀδελφὸν] Lot and his possessions, together with the women and the other people.” Lot, of course, was actually Abraham’s nephew, but here we see ἀδελφὸς used in the context of extended, rather than nuclear, family.

Over-emphasis on the nuclear family in contemporary Christianity undermines our ability to understand the kinship language of the New Testament. Attention to the way that ἀδελφὸς is used in both the Septuagint and the New Testament will enable us to better grasp the actual meaning of New Testament kinship language.