Is this a recent problem since he installed the hive or has it always been an issue? I have a hive in a suburban area but there hasnt been a significant increase in bees around due to my hive. My flowers were covered with bees before i set it up, and i still see plenty of bees not from my hive (different colouring) in my yard.
Normally a surburban bee keeper will have a bred queen bee from a more docile strain… it would be unusual for his bees to feel threatened by you so far from their hive. I can sit a yard in front of my hive without the bees taking an interest in me.
Do you know why they are coming to your back yard? Is it for water? I had an issue where my neighbours dog was stung a couple of times because the bees were using her drinking bowl.
Are they normally flying aggressively around you or is it normally a sting on the foot when they’ve been accidently trod on? If your lawn is covered in clover there’s a good chance of stepping on a bee.
The other thing that is worth considering is flight path. Bees from the hive will typically follow the same route from the hive. If the bee hive is near your boundary and facing it there is a chance their habit is to fly across your yard. This can be disrupted by your neighbour putting up an obstacle a couple of meters in front of the hive to force them to fly up above head height before they set off.
You should be able to resolve the situation amicably as it is definitely possible to have multiple hives in a suburban area without impacting the neighbours. We’ll do our best to help you out.