You do know Zac carries a gene for blue eyes right,? Diana has blue eyes. Did people miss simple science? Two brown eyed people can have a blue eyed child if both carried a recessive gene for blue eyes which obviously Zac already does and Kate must too. Now if Zac and Kate were both blue eyed and had brown eyed children that would be different as two blue eyes can’t produce brown.
But yeah suggesting a dna test for that then I guess my dad should too since both my parents have brown eyes and I’m blue eyed.