Yevamot 36: The Sadness of Yibum

On Resh Lakish, in contrast to R. Yochanan - on the 3 times we follow Resh Lakish. Including regarding inheritance regulations, as compared to those of a gift. Also, what happens if there's yibum between a yavam and a yevama before waiting to see if she is pregnant from the brother who died....? The Gemara debates them needing to divorce and separate forever, or separate until they know if there's room to permit them to be together...and whether the sages agree or disagree. Including when the child does or doesn't survive for 30 days or more.