Emily Feather and the Starlit Staircase (Emily Feather #4)

Emily Feather is an ordinary girl in an extraordinary family of fairies. When Emily finds out her adopted mother is pregnant, she can't help feeling upset. This means there will be another brother or sister who will actually belong, unlike her. They will also be a fairy and have magical powers.

Then her brother, Robin, takes Emily through one of the enchanted doors to show her a magical alternative life, that might have been had Emily not become part of their family...