I too was surprised to learn that siblings can be <very> different.
The most fun cross I ever bloomed was BEHOLD A LADY X CELEBRATION SONG.
12 surviving seedlings, nearly all strikingly different. Red-bearded
white, yellow amoena, pink amoena, grey self, brown self, pink stds near
white falls, variegata, the rest different blue to lavender neglectas &
<I was very astonished that iris siblings can be so different.
Greetings from Germany