Hi Megan, Even if you don't buy all those certs I suggested, you need to see the ones which take you back past the earliest Skillicorns found so-far.
Those are:
Death:
18349/1945, SKILLICORN, BERTIE PHILIP AUBREY, [father]: PHILIP AUGUSTUS [mother]: SARAH, [place]: MARRICKVILLE.

Marriage, in 1877:
2176/1877 SKILLICORN PHILIP, [to]: PATTERSON, SARAH, [at]: BATHURST.

The death cert will give crucial information about Bertie's parents, and the marriage should show whether this is the right Philip [from the death cert.], Philip's age and occupation, and whether he was born in the IOM or elsewhere, plus full names of both his parents plus father's occupation.

No need to guess when these excellent NSW records are available for a small fee.

Sue