Hi
You are clearly a very caring and conscientious owner. There are indeed piggies who struggle to get along with others and who prefer not to share their territory with others.
Generally we recommend to consider next door companionship, with both piggies having their own territory and a grid divider that allows full interaction through the bars for those piggies that still recognise themselves as guinea pigs and that do not just totally ignore any others of their kind, provided you have the space for a divided large cage but there are exceptions with piggies who are so fear-aggressive that even that upsets them greatly.
But you could even consider another single, difficult to bond sow as long as your neither party can jump over or wiggle through the cable-tied grids - if needed with a plank over the cage along the divider on your boy's side.
However, if any of several efforts have been unsuccessful and your boy has been each time happier being back on his own with plenty of attention from you, then keeping him as a single is OK.
The important point is that you have given your boy several opportunities to have a say in how he is happiest and that you have not just imposed the decision on him.
You may find this guide here helpful. It is taking a differentiated look at singles in different circumstances and also contains a chapter about how to spot when our piggy is transferring their social needs onto you.
Introduction
1 When is a 'single' really a single?
- Bought singles
- Fallen-out and aggressive piggies
- Bereaved guinea pigs
- No interest in other guinea pigs
- Disabled and special needs guinea pigs
2 Companionship options (with pros and cons)
- Dating
- De-sexing (neutering or spaying)
- Living alongside
- Buying a baby companion
3 Caring for single guinea...
My Beryn, who was found wandering the grounds of a cricket club in Wales in 2017 and who must have been somebody's much loved single piggy (I suspect a domestic abuse scenario), took one and a half years to find a companion who wanted her and had the patience to help her work through her massive fear-aggression issues. Sadly, their close friendship only lasted one year; Betsan passed away very suddenly just before the pandemic. Beryn ended her life as a next door piggy to the neutered boar that had been the closest fail and his new wifelet.
I have also had quite a number of old ladies who would not accept new company after the loss of their last companion(s) and who preferred to conduct ongoing feuds with their neighbours through the bars...
Beryn and Betsan