Brothers in Christ should suffice.
A couple shacking up and having babies out of wedlock, and refusing to marry, aren't practicing Christianity in any way, shape or form. They way they are living seems to be violating Jesus Christ's most emphatic teachings and commandments on marrige, adultery and fornication.
I think the Town is absolutely right in asking them to get married to legitimize their family and bring a respectable example into the community. If more Towns had this courage then we'd see a lot less of this sort of degredation of the family, (and the female body), in America.