Here are my lists:

[pygmy]

Edgar Ivo
Ivo Edgar
Hector Ivo

Greta Ivy Rose
Maeve Ivy Rose
Isadora Ivy Rose

I have two older sons who are Finn and Louis.

Which do you like and which fit best with my sons' names?

Love Ivo, and Isadora!

The meaning of Hector (bully, torment) would put me off, as would the lack of nicknames (Heck?).

Edgar and Maeve for me

I love all of them!

They all fit nicely with your other DC,and are all lovely in their own right.

I can't even choose a favourite,which is very unusual for me

I like the NN Tor for Hector....but the meaning does put me off a bit.

Yes, the verb hector puts me off a tad too. I think I would still use it though!
I don't think I'd use a nickname. Louis is always Louis; never Lou.

I would use Dora for Isadora by the way. Not keen on Izzy!

Edgar and greta are my favourites

Dora is much nicer than izzy,I agree.

Edgar is lovely,but I don't like Ed.

On reflection I like Ivo and Greta best

Good choices :)

I would pronounce it Eye-vo, not Eee-vo by the way!

I like Ivo and Isadora

I think of Hector as in the Illiad - such a wonderful character!
Isadora is also lovely!

These are great choices - like all of them, and all go with with your dcs. If I had to choose I'd go for Greta and Ivo.

Edgar & maeve

Hector

Maeve or Isadora both lovely but Maeve pips it for me.

Don't like Ivo or Ivy and Rose just seems to be a default add-on tbh.

Ivy and Rose are our grandmothers' names; we'd very much like to honour them, so they are a must.

My dd's middle name is Greta. Gorgeous name.

Isadora or Greta, not keen on Rose or any of the boy names though, sorry.

I think they are all really, really lovely.

My favourite boy's name is Ivo, just pipping Edgar and a little ahead of Hector.

For a girl, I love them all equally. (Sorry, no help).