Tractate Yevamot - Chapter 14 - Mishnah 8

If two brothers of sound senses were married to two strangers, one of whom was of sound senses and the other deaf, and the brother of sound senses, the husband of the deaf woman died, what should the brother of sound senses, the husband of the woman of sound senses, do? He must marries her and if he wishes to divorce her he may do so. If the brother of sound senses, the husband of the woman of sound senses, died, what should the brother of sound senses, the husband of the deaf woman, do? He may either perform halitzah or yibbum.