Please confirm that (i) Bais Shamai is of the view that Maamar is deoraisa even when there is only a single Yavam, with a nafka mina being whether it can create a safek nisuin for yerusha purposes when there is a single Yavam, and (ii) the various Yerusha issues that arise with respect to a child who is a safek of being a child of the decedent brother or alternatively of the Yavam are issues that arise as a matter of law and do not depend on actually being raised by the litigants.
Elia Fischer, Atlanta, GA
There doesn't seem to be any reason that Beis Shamai (according to Rava on 39a) would not say this when there is only a single Yavam. I also agree that this seems to be a matter of law, not a matter of claims which have to be made by the litigant.
All the best,
Yaakov Montrose