May I mention another apparent anomaly between the info gleaned from the online indexes and the Ancestry trees that include Agnes and Mary FIRTH.
The NSW BDM index has a Mary Ann LONG’s death registered 1941. There’s no one else by that name on that index in that year. The index does not have the given names for her parents, and instead, the compiler has at least noted other info from her dc registration. So, we can read that Mary Ann LONG was 88 years of age, and she died in Sydney. I ‘know’ this because the Ancestry tree cites a source, and the ref no. they cite is 22108. That number is the NSW BDM reference for a death cert for Mary Ann. I presume the tree owner actually has an official transcription or a legal copy of that document.
However, the Ancestry tree has Mary Ann’s age at death as 78 years, rather than the 88 years the NSW BDM index has. To me, this could be fairly significant. It puts Mary Ann as the older of the two sisters, and I recall that it was Mary Ann who married before Agnes married. If Mary Ann was born 1863ish, then she was 16ish when she married, so she was not yet old enough to give consent to her own marriage, and she needed someone else (her guardian) to give that consent for her. If she was born 1853 ish, then she had reached her majority well and truly and could consent herself.
Mary Ann FIRTH’s marriage to John LONG is indexed at NSW BDM for 1881, and is ref no. 4905, registered district of Gulgong. The Ancestry tree has a date for that ceremony, 24 December 1881.
These NSW BDM registrations are actually available to any member of the general public to purchase. Official transcriptions of any registration you can find at the online index for NSW BDM are available for around $20 each from any of the three authorised official transcription services. You do not need identification to order these. You do not need to be a family member to buy either a copy or an official transcription of these official records.
I think that Mary Ann FIRTH’s 1881 marriage registration needs to be checked and yes, there may well be blanks on that official registration. If so, then after you have purchased the document please please hasten slowly and search out the original parish registers. Of course, this is assuming you have long known that this Mary Ann is Agnes’ sister.
But I do think it is often sensible to hasten slowly and methodically through and don't jump ahead of ourselves. There's no point in joining dots way ahead, until we join the dots immediately in front. Otherwise we can end up on a dot with no where to go.
Cheers, JM