Where do you stand on background relationship tagging?

It seems like the sort of thing where whichever direction you take it's not going to please everyone, but if you have a relationship occurring entirely in the background do you tag it in relationships or additional tags?

On one hand, it is called "Relationships", but if it's there, are people going to assume a bigger focus than it actually gets?

I've only had to do it once, but I used a "background [character/character]" tag, so it's there but people will know it's not an important aspect.