We have a [name_u]Theo[/name_u] (not Theodore). Expecting a little girl. Bonus if her name starts with an R or an E. I prefer 1- or 2-syllable names, but occasionally a 3-syllable name is fine.
Here is my list (more or less in order with favorites at the top). Please comment on your favorites (or least favorites!) and feel free to add!
I love [name_f]Ada[/name_f], [name_f]Liv[/name_f], [name_u]Skye[/name_u], [name_f]Willa[/name_f], [name_u]Riley[/name_u], and [name_u]Quinn[/name_u] with [name_u]Theo[/name_u]!
I really like [name_f]Ada[/name_f] and [name_f]Willa[/name_f] for a sister for [name_u]Theo[/name_u]. Some ideas: [name_f]Belle[/name_f], [name_f]Eve[/name_f], [name_f]Lucy[/name_f], [name_u]Noa[/name_u], [name_u]Robin[/name_u], [name_f]Vera[/name_f], [name_f]Zoey[/name_f].
[name_f]Ada[/name_f], [name_f]Liv[/name_f] and [name_f]Willa[/name_f] are my favourites and I love them with [name_u]Theo[/name_u]! [name_u]Ellis[/name_u] is quite nice too.
[name_u]Theo[/name_u] & [name_f]Willa[/name_f] are sheer perfection to me!
I also like [name_f]Ada[/name_f]! [name_f]Liv[/name_f] would be nice but a bit wordy for me.
[name_f]My[/name_f] first thought was [name_u]Theo[/name_u] & [name_f]Ella[/name_f] which is similar to your [name_u]Ellis[/name_u]. And I second [name_u]Ruby[/name_u] which would also be such a stunning match for [name_u]Theo[/name_u], and you might also like [name_f]Rosa[/name_f]