A [boy] nine years and one day old who cohabited with his yevamah, and then cohabited with her co-wife —- he has disqualified [them] to himself. R' Shimon says: He did not disqualify.  [If] a [boy] nine years and one day old cohabited with his yevamah and [then] died, she performs chalitzah, but may not be taken in yibum. [If] he married a woman and [then] died, she is exempt.