Wiktionary
become of
vb. (context transitive idiomatic English) to happen to, to occur to.
Usage examples of "become of".
What shall become of us at the end, if at the beginning we are lukewarm and idle?
I must see what has become of the Pattern I drew to the sound of pigeons on the Champs-Elysees.
They'd both be at the back of the north wind directly, and what would become of the other places without them?
Maybe there is some that want to know what has become of the gold and jewels that he buried in the hill of Hobbiton, as I hear?