The wild ancestor species lives in small groups in tunnels and dense undergrowth, but a number of them living close to each other that make the joint trip to their current feeding grounds together during early morning and evening for added safety; guinea pigs are territorial about their own patch, but they are also wired to eat as a community. Even though our own guinea pigs have been domesticated and outbred for 3000-6000 years, these social behaviours have remained.
I see the same with the different small groups and pairs - they are very protective over their own pens and who they are bonded with but they also have an overall boar hierarchy and they come out as a unit to eat all at the same time in the mornings and late afternoon; the same goes for grieving.
Yours have obviously decided to see you as an uber-pig and to take their cues from you as they the guidance of their own species elders that would teach and socialise them until they reach the teenage months.
Understanding Prey Animal Instincts, Guinea Pig Whispering And Cuddling Tips