Tutoring siblings: together, or separately?

There's no universal right answer here, but a couple of patterns hold up well in practice. Siblings close in age and level, in a subject like Maths where pace matters more than personal expression, often do genuinely well learning together; there's a natural, healthy bit of competition, and a tutor's time covers two learners in the time it'd otherwise take for one and a half sessions.

Subjects that lean on personal response (English essays, a Modern Language's spoken component) tend to work better one-to-one, since a shared session can make a less confident sibling hold back rather than commit to their own answer.

A meaningful level gap (one sibling at National 5, one at Higher, even in the same subject) usually argues for separate sessions regardless of subject; the pace mismatch outweighs any efficiency gained from combining them.

If you're not sure which your family fits, it's a completely reasonable thing to ask a tutor directly; most will have a view within the first session or two of trying it either way.