Cranmer on incest - just wondering...?

Returning home from the Banner Conference, there's lots to catch up with.  Archibishop Cranmer is always worth a look; scroll down to April 13th ( can't work out how to link directly to this one) and see his comment on the case of Patrick Stuebing.  It's a sad case: Patrick only ment his sister after thy were grown; they fell in love and have four children together.  He argued that the law against incest discriminated against him - and he lost.  As Cranmer says, the law apparently does have the right to a say about what is allowed in the bedroom.  'In matters of sexual expression we are not free to do as we please.'

Hmm.  I agree, of course.  But I do wonder - don't you? - if incest between two brothers would have been deemed illegal?