What's the Name of That Book??? discussion

My local library had a copy that was (I believe) 3 books bound in one copy. There were three siblings but the POV centered on the middle boy who had a green eye and a brown eye. His older sister had 2 brown eyes and his younger sister had 2 greens eyes and they could see the magical world with their green eyes. The dragon could be controlled by it's true name but only 3 times per person. The boy may have hidden the dragon in his treehouse, and maybe the youngest child's name was Alice?? I'm not sure, anybody know?

The Eidolon trilogy by Jane Johnson? The first one is The Secret Country.

That's the one!!! Thank you so so much:)

Wonderful! You're very welcome.