誰可以告訴我這句英文的意思?

那就成為 Since he lives with your sister，I assume his father must have died.
因為他和你姐住在一起，我就認為他父親一定已經過世了。
(前一句是因，後一句為果) 改過的句子，論結構、語意皆比原句清礎。

2011-11-16 13:33:51 補充：
請問版大您在說誰是用網站的翻譯？我個人是從來沒用過。還有，你是否有看清礎我改過的句子和原句的不同？！

原句的時間點好像有點怪怪的，既然後半句是現在式"lives"，為什麼前面會用到過去式"assumed"?

I assumed the father must had died, since he'd been living with your sister.
I assume the father mush have died, since he's living with your sister (or since he lives with your sister).