Note: the above are all books with LGBTQ MCs in which siblings are central to the plot and theme (and in some cases also have a POV), not books with siblings who are LGBTQ. The latter will be a separate post.
And I Darken by Kiersten White
Ramona Blue by Julie Murphy
I’ll Give You the Sun by Jandy Nelson
Jerkbait by Mia Siegert
Little & Lion by Brandy Colbert
Bonus: Coming in 2018, Girl Made of Stars by Ashley Herring Blake