Man of the House Trilogy, Book #2. It is filed under taboo incest, and runs about 31200 words. 4.5 out of 5 from 191 readers.

Others under taboo incest Older Sister's Embrace, My Lingerie-Loving Sister Moves In and 2 Moms, 2 Sons... Ch. 5, and 9 more.

Or keep going.