Aligning posts of dissimilar fences at a corner

I’m replacing both an adjoining neighbour fence (timber) and a boundary fence (aluminium). Where the two fences meet at the corner I’m unsure how to set the posts. It’s my understanding that the two posts should not be set together as you then wouldn’t be able to replace one without having to dig up the other as well. However I don’t want a large gap between them either. I’ve seen corner posts close together (exactly together in some cases), how is this done without setting both posts together?
cheers