Quite a racket around 5am. Seconds before this Rolf darted at a cub(?) with his jaws open - I didn't realise until rewatching this that there were 3 foxes, so that was presumably the "black sheep" cub of his (or a stranger?), who takes off to the left. Niam seems perplexed and keeps a distance the whole time.
Even stranger, the night after this (last night) Rolf came down in the evening but moments after he left the mystery cub made a sudden appearance, at one point watching me closely from the top of the garden. I left some food which s/he would run in and out to snatch pieces of, again and again. They're the polar opposite of Niam. And then moments later Niam appeared, and they were both in the garden at the same time, together on the steps only briefly (I had hoped with his brother around, the other cub would feel more confident staying when I came out, but he hid in the bushes while Niam danced around me).
And then once they'd left, minutes later the cat appeared!
I believe Niam's sibling will be chased out of the area soon, while Niam has been raised to accompany his father. It's cold and difficult for them at the moment, so it's intriguing how the unfamiliar cub is apparently keeping closer to his father now.