I was wondering if Margaret could be the daughter of William Mylrea and Elinor Caine. This Margaret was born in 1813 (the daughter of Thomas Mylrea & Elinor Corlett was born in 1806 - so a bit older than usual to be getting married whereas the former girl would have been 25, which is about average). Margaret & Daniel both have death certificates in the NSW BDM. From memory they died quite soon after arriving in Australia but I haven't seen the actual certificates. I'd be very keen to know what you come up with.