Help with Skrzynecki's '10 Mary Street' please (1 Viewer)

[bubblemachine]

Hey I'm wondering, about 'Ancestors,' at the end of the poem where he talks about naturalization and what not, what do you make of it? do you think he's suggesting that although they've been naturalized they're not assimilated into the Australian society? or am i thinking too much, and its just kinda saying how much being naturalized has meant to them?
i also need help with interpreting the last three lines, "inheritors of a key/that'll open no house/when this one is pulled down." thanks!