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?

[shoobidoo]

Love Ivo, and Isadora!

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

[MerryMingeWhingesAgain]

Edgar and Maeve for me

[FriggFRIGG]

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

[FriggFRIGG]

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

[pygmy]

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!

[Mama1980]

Edgar and greta are my favourites

[FriggFRIGG]

Dora is much nicer than izzy,I agree.

[FriggFRIGG]

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

[FriggFRIGG]

On reflection I like Ivo and Greta best

[pygmy]

Good choices :)

[pygmy]

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

[Beatrixpotty]

I like Ivo and Isadora

[fertilityFTW]

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

[TenthMuse]

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.

[NowPlayingZone]

Edgar & maeve

[RemusLupinsBiggestGroupie]

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.

[pygmy]

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

[MamaBlue4]

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

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

[mathanxiety]

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).