Have I correctly used all the phrases (enclosed in the parentheses) using ‘since’?

Have I correctly used all the phrases (enclosed in the parentheses) using ‘since’?

1. Fredlyn said that it had been 18 years (since her father’s disappearance, since her father had disappeared).

2. Mavelyn said that (since her parents’ death, since her parents had died), she had been living with her grandfather.