Yerushalmi Yevamot 13:12 ירושלמי יבמות י״ג:י״ב

MISHNAH: A hearing wife and a deaf-mute. If the levir had intercourse with the hearing woman and then had intercourse with the deaf-mute, or his brother had intercourse with the deaf-mute, the hearing woman was not disabled. If the levir had intercourse with the deaf-mute and then had intercourse with the hearing woman, or his brother had intercourse with the hearing woman, the deaf-mute was disabled.

HALAKHAH: “A hearing wife and a deaf-mute. If the levir had intercourse,” etc. Even if he did not have intercourse with the hearing woman, the deaf-mute is disabled¹¹⁶In the presence of an underage widow, the candidacy of the deaf-mute widow for levirate is not executable. As an earlier Mishnah stated, intercourse with the deaf-mute does not free the underage girl. The candidacy of the deaf-mute could be resurrected only if the underage girl died before she was married by the levir.
It is obvious that if the case involves a biblically married woman and a deaf-mute or an underage girl, the same situation applies.. If he did not have intercourse with the hearing woman and she died, he would have been permitted the deaf-mute. But now that he did have intercourse with her, even if she died he had disabled the deaf-mute.