To leave DC home alone

[WhisperingLoudly]

Three DC. Older two (years 6 & 7) get left alone/together periodically. Only during the day and never for more than an hour.

Youngest DC is year 1 - AIBU to throw her into mix and leave oldest DC and youngest DC alone together for an hour or so?

No. It's unfair on the oldest child.

I would feel happy to leave the 5 year old with them whilst I nipped to the shop for 10 mins, but probably no more than that for at least a year or so.

I wouldn't. But then I probably wouldn't leave the older two for that duration by themselves either (but I'm in the minority for that)

I leave my 14 & 12 year olds together, and have done since they were 13 & 11 but not really younger except in emergency or for v short time. Wouldn't leave a 11/12 year old in charge of 2 younger siblings.