I am not very familiar with the concept - it only happened once to be invited in such a wedding and I have also heard of another.
But how is it possible to invite adults only? I mean if parents go to the wedding then who is supposed to look after toddlers, babies etc. ?
Is it a way to say to people “we invite you but please don’t come?”
We have no family/support around and this invite sounds a bit weird and discriminatory … If you want someone to share the joy and happiness with you then you must welcome his other half and, of course, children under 18 years old! Where are they supposed to stay while their parents celebrate with you?