Reference for Yevamot 44:16

וכ"ת אחותך דכתב רחמנא למה לי מילתא דאתיא בק"ו טרח וכתב לה קרא כתב רחמנא היא

Our Rabbis taught: He who has intercourse with his sister who is also the daughter of his father's wife<span class="x" onmousemove="('comment',' I.e., the offspring of a lawful marriage. ');">¹⁵</span>

Jastrow

Jastrow