Thank you Ruskie, Ennael and Jamjar
I can confirm that you have identified the family and aware that other children were born Seymore Vic. Hartley NSW , and Thebarton South Australia.
Martha ( Knight ) Longstaff born Thebarton. was the grandmother of my late wife.
I think Lucy , her mother died following birth of Martha , who was then reared by Grace Knight a sister of Lucy who had married Robert Grigg.
I assume Thomas and Lucy probably landed Queensland and initially lived Ipswich , but possible they arrived elsewhere.
They do not appear to be listed on the site cited by Ruskie.
Robert Grigg and Grace ( Knight ) arrived Port Adelaide 16 Dec 1856 on "Monsoon".
Martha Knight married Edward Albert Longstaff. She died Yarraville Victoria.
All I need now is the passenger list for Thomas and Lucy.

Quite possible first child on the way.
Sorry if any confusion.
Rex