Welcome to the forum
What you are describing is normal dominance behaviour. They are getting on absolutely normally and don’t sound, from what you’ve said, to have bond issues.
If there is further information and issues which give cause for concern for their bond, then do let us know and we can help further
You can add another sow if you wish but it won’t change or stop any behaviours you see now. It won’t make them get on any more than they already do.
A sow trio absolutely can work provided they all want it to and are character compatible. However there is the consideration that a trio can mean one piggy gets left out while two remain close.
If your current do not accept a newcomer into their pairing, which is always a risk when bonding on spec, then you need to be able to have two separate cages and then to get a fourth piggy to bond with the third piggy.
Do you have a large cage? 150x60cm or a 4x2 c&c is recommended for two sows.
For three it needs to be 180x60cm or a 5x2 c&c
Do all hides have two exits? We don’t recommend any single door hides as one piggy can trap the other inside.
Do you have multiple resources? ie at least two hides, two hay piles, two water bottles.
The temptation is always there when you have two adorable and happily settled guinea pigs to stick in another one into a generous cage or to merge your two pairs of guinea pigs. This however can rather easily end in disaster if you do not respect your guinea pigs and their social needs and quirks. Bonding is not quite as easy as introducing your piggies for a happy ever after for you!
Even your pairs may not always be as stable or happy as they grow older. Not all singles will immediately fall in love when seeing another piggy. Some can be actually rather challenging to bond.
Here is more...
Overview
1 List of dominance behaviours in ascending order of aggression
2 What may cause this type of behaviour in boars?
3 When do you see these behaviours in sows?
4 What can trigger fall-outs?
5 Further helpful guide links
I thought it may be handy to have a sticky on typical dominance behaviours for a reference - hopefully it may help humans understand guinea pigs and their behaviour a bit more and hopefully prevent some avoidable problems!
1 List of dominance behaviours in ascending order of...
Overview
1 Sexing on arrival
2 Important reproductive Facts
- Start of making babies - seasons - lack of menopause
- Pregnancy
3 Sows in season
- How a season runs
- Strong seasons (snap seasons; the social role of strong seasons; problem seasons)
4 Behaviour and social aspects
- Bonding (Possible combos; acceptance and dating; special bonding aspects)
- Typical sow dominance...
