So the Find Familiar spells says that the caster can see and hear through the familiar's eyes and ears. I'm wondering what happens if the familiar encounters an illusion, say a Minor Illusion, when this is happening. Who makes the saving throw to disbelieve the illusion, the familiar or the caster? Or do they each get a saving throw?

So the Find Familiar spells says that the caster can see and hear through the familiar's eyes and ears. I'm wondering what happens if the familiar encounters an illusion, say a Minor Illusion, when this is happening. Who makes the intelligence check to disbelieve the illusion, the familiar or the caster? Or do they each get a check?