Help me name this book

[myusernameisusername]

About an Australian child migrant called Arthur hobbs and he gets sent away to Australia without his sister Kitty he ends up living on a farm where he and his friend escape and are helped by aboriginals i think that's all I can remember about it

oh and he later has a daughter who sails to London from hobart to look for kitty after her dad dies and she finds her also has something about a key kitty gave arthur before he got on the boat to Australia cant remember the name of this book or author

Anyone ??

Alone On A Wide, Wide Sea by Michael Morpurgo, possibly?

yes thank you

Yay!!

Bought it on ebay for £3 happy bedtime reading till 7am