Oh, I love middle name [name_u]Marlowe[/name_u] for [name_u]Ruby[/name_u]!
I know a [name_u]Ruby[/name_u] whose little brother is [name_m]Zane[/name_m]! from your list I’d pick, in order of preference:
[name_m]Jasper[/name_m]
[name_m]Ezra[/name_m]
[name_u]Theo[/name_u]
I love [name_u]Ruby[/name_u] and [name_m]Jasper[/name_m] together
Oh darling [name_u]Ruby[/name_u]. I’ve got a real soft spot for that name. And paired with [name_u]Marlowe[/name_u]…to die for!
I like [name_u]August[/name_u] a whole lot. The girls I know named [name_u]Ruby[/name_u] have brothers with more “throwback” names (like [name_u]Theo[/name_u] and [name_m]Jasper[/name_m]'s style) but I don’t think this is necessarily essential.
Here are some of my ideas, some I think would even work for middles with your current list, which is great!