This is how it always is by Laurie Frankel

 Rosie and Pen had 4 sons and tried once more in hopes of getting a daughter. What they got was Claude, who was born a boy but wanted to be a girl. And so begins a long (and frequently funny, sometimes sad) journey as the family tries to navigate these unknown waters. I did love the family in this story, because they were very supportive of young Claude/Poppy, whoever he/she wanted to be. In a note at the end the author says she has a child who faced a similar journey, though this book is fiction.