Yes, they are real.
If you are referring to their often big pupils, this is because I take these photos at night time. As you know, anyone's pupils dilate as it gets darker. It's as simple as that: I mostly shoot when it gets dark, because I love the big pupils. I also like to photograph their facial expressions when they are playing at night time, which makes for even bigger pupils.
Here you can see Izzy's big pupils in action:
Een bericht gedeeld door Izzy & Zoë The Cats (@izzyandthefluff) op 1 Apr 2017 om 3:14 PDT
And here you can see Zoë's:
Een bericht gedeeld door Izzy & Zoë The Cats (@izzyandthefluff) op 27 Apr 2017 om 10:38 PDT
If you are referring to their eye colour; variations in their eye colour are caused by different lighting situations. Just take a look at their eyes in this video below and see how the colour changes depending on how the light hits their eyes (especially Izzy's, who moves more):
Een bericht gedeeld door Izzy & Zoë The Cats (@izzyandthefluff) op 31 Okt 2017 om 12:59 PDT