These days we tend to see the New Testament's use of family language to describe fellow Christians - especially brother and sister - as conventional. Indeed gone are the days that Christians in the UK routinely refer to each other as brother or sister.
But for the early Christians this was anything but routine. One of the revolutionary aspects of their new faith was that through Jesus people who were not related became kin. That Paul thought this was worth stressing is seen in the fact that in 1 Corinthians, a letter written to fractious and divided community, he uses sibling language 39 times to stress the closeness of the bond that exists between Christians. He especially uses it when he wants to draw attention to behaviour that is inappropriate to our new family status - such as in 8:8-13 where he uses the word brother four times.
At the end of Romans in a list of greetings to various people involved in various house church groups across the city, he also uses the language of family - Phoebe is 'my sister', Rufus' mum has 'been a mother to me also', many in the list are described as 'beloved' - hardly the language we use of work colleagues.
And he uses it to stress the need to welcome one another (15:7). The situation is probably this: many of those named - especially the Jewish ones - are Jewish Christians who have recently returned to Rome having left in the late 40s when the Jewish community or parts of it were expelled from the city by Claudius. It's possible that those expelled were mainly Jewish Christians because historians of the day tell us that the expulsion happened following disturbances instigated by 'Chrestus' (possibly an early Latin miscontrual of Christ).
Now they were returning and needed to welcomed back into the predominantly Gentile house churches that were thriving in the city. Paul says these people - of different race, background and dietary behaviour - are brothers and sisters, family, kin and so should be welcomed with open arms and offered hospitality. It is possible that Romans 12-15 has been written with this in mind to ensure the family life of the churches in Rome is built up and the newcomers welcomed and included in the various groups that met around Rome.
For us it reminds us that we are family. If we are followers of Jesus, we are blood relatives of all the others followers of Jesus - whether we get on with them or not. We need to welcome one another, be hospitable, seek to help where we can and not discriminate against those who are new or different from us.
God gloriously calls us to be one family in his son Jesus - as Paul reminds us in his great Bible study in Galatians 3 which culminates in the ringing declaration of 3:28.
It also has something to say about church and post-church groups which I'll reflect on in a sbsequent post.