My FI has family friends who are a lesbian couple. We are inviting them to our wedding. They are unmarried and have not had an official commitment ceremony, and I'm not sure whether it is a personal reason that they remain unmarried or just because it is not legal in their state. However, they have been together for 20+ years. I'm debating how to address their invitation.
Putting their names on one line with "and" between them seems presumptuous if they are simply choosing to remain unmarried/not make a formal commitment.
I don't want to discount or belittle their long relationship by putting them on separate lines in the case that they are unmarried only because they cannot marry.
I feel like either way I go I have the possibility of offending them. Any advice?