Researching: Bosse - Eggers

Hello everyone,
I am doing some research for a friend and I am wondering if anyone has any iformation on the follwoing:

August Bosse born 22 August 1832 at Doernten, Hannover. His parents were Christoph Bosse & Sophie Loose/Losse.

Christina (Dorothea) Eggers born 6 January 1840 at Doernten, Hannover. Her parents were Christian Eggers & Gertrude Sievers (Sievert/ Stewers).

August and Christina came to Australia around 1858.

Where can I start searching or writing too. Thank you all!
Atina Marks. Australia.