I can appreciate
Ignatius a lot even if it isn't my cup of tea :) I think the nn "
Iggy" would be rather adorable.
I think you've listed some great ideas for siblings. I particularly enjoy
Arabella. Some other sister's name could be (following the tone of uniquely named Saints):
ApolloniaAuria
BibianaJulittaOdilia
and brothers:
I love your
Ambrose,
Maximilian, and
Caspian, and also
BarnabasBenedictCassianCorneliusCyprianEdwinFerdinandFinnianMariusOliverOttoRemi