Hi Jane,
A Big Welcome to RootsChat!

Can you tell us any more about these people please? I am not seeing anything to fit. No birth listed for Daniel but looking at the names they may well be Catholic and we find in our early history a lot of Catholics did not register their children. They felt baptism was far more important.
There is no marriage listed for a Daniel SULLIVAN and Mary HALPIN - there is however this marriage
SULLIVAN Michael full age single father unrecorded =
HALPIN Mary Full age father unrecorded 11 Jun 1850 Catholic Church Adelaide Dist Ade 8 196
Cheers Kris
