I've been checking all the bird sites to try to find the answer, but haven't so far.
They do say that few small birds re-use a nest in the same place, maybe so they don't attract predators, even for a second brood, so maybe it is a different pair if the same is true for nest boxes. I'm not sure great tits even have the same mate two years running - but I'm no expert
Kate Garroway-Care at home costs
Good Morning Good Friday 29th March 2024