Incest between shapeshifters and aliens is weird. That's the plot of DirtyPurpleAndalite's story “How Far Will I Go?” found at fanfiction.net featuring cousins Tom and Rachel from the Animorphs series. Attempting at eroticism and escapism, the piece fails both.
Cousin Tom walks in on naked Cousin Rachel, and threatens to kill her friend if they don't have sex. After token resistance, she discovers her desire for rolling in the hay with relatives and calls her vagina a “honey pot.” This is all lead up for an event which mercifully never happens, though one DirtyPurpleAndalite was obligated to deliver. Writing Animorph incest fanfaction means your readers are looking for communities and stories that:
A. Accept their interests
B. Involve incest. Big surprise there.
No half measures. “How Far Will I Go?”'s content is like its story, all foreplay and no sex.