I seem to recall something about Granville worrying about a repair on the roof (presumably meaning Arkwright was no longer in charge) around the time Leroy was conceived.
Presumably Arkwright, being Arkwright, would be in charge until he died.
I think Leroy was supposed to be about 25 at the start of show - the same age David Jason was supposed to be in the very original OAH pilot.
The SOAH pilot was in 2013.
It's quite possible Arkwright died around the late 1980s.
I also seem to remember something about Nurse Gladys (and possibly other female neighbours, memory is going) looking after the very young Leroy - again suggesting that Arkwright wasn't around.
I don't believe he would have known Leroy.
But this is complete speculation as there simply isn't enough information on the show.
I think this crude and inaccurate guesswork is based on the info given in SOAH pilot (and possibly the Series One episode where Leroy's mother returns). Not too sure. Not watched it lately.