Hi Lady Di,
Biographical Database of Australia, annual subs about $30.
https://www.bda-online.org.au/ Here's a possible starting point to look out for live twin births with both babies surviving in that era.
Samuel CRAFT 1763-1833.... per Salamander - seems that he had several NSW born children, including twins with Elizabeth DAVIES. The twins were William and Elizabeth born 1800. William married twice - second wife was Ann McGRATH, daughter of Elizabeth SOMERVILLE.
Re missing lines... Firstly I looked at marriages for 1812 for volume 3A ... so will hopefully obeying Lachlan Macquarie's General orders issued 1810 ... See Sydney Gazette 22 September 1810 page 1.
https://trove.nla.gov.au/newspaper/article/628072 - it was meant to cover 'all births and deaths' ... not just baptisms and burials conducted to C of E rites.
Volume 3A for 1812 marriages sample test run only, sorting the online display by Registration number from highest with district as C* (reason ... to avoid results coming up for other volumes of line 1 etc, volume 3A will have the most entries as it is for NSW chaplains receiving transmitted records as well as actual ceremonies held at St Phillips).
(district of) CH - line 2230
CB - line 1550; 1433; 1431; 1427; 1422; 1418 - 1416; 1406-1405; 1403;
CC - lines 1439, 1438; 1434; 1428; 1420 - 1419; 1415- 1412; 1408-1407; 1404;
CA - lines 1437 - 1435; 1432; 1430 - 1429; 1426-1423; 1421; 1411-1409; 1402 - 1400;
CH is Christ Church, Newcastle.
CC is St Matthews CofE, Windsor
CB is St Johns Parramatta
CA is St Phillips
That's not saying that the ceremonies were held within the church building, rather that the parish register for that district lists the ceremony. So we need to remember that both St Johns at Parramatta and St Phillips in Sydney Town were where NSW Chaplains were conducting C of E services and also were recording transmitted records of births, deaths, churchings and marriages ... umm... so volume 3 was not just holding C of E info, but of course the bulk of the info was C of E as there were not too many clergy of other denominations in the colony.
Comment ... I have only taken a very very small sample, but it seems to have not omitted any line numbers there. I have confirmed that I can still 'sort' each of the NSW BDM column headings separately. This is very handy when looking for missing numbers or looking for null info in a cell.
I will wait for some of my rellies phoning me for suggestions for looking for 1796 era baptisms... I have searched this morning online and yes, our Hawkesbury family from that decade - yes all of 'our' baptisms are still listed at NSW BDM ...
JM