Just Mom. When I was eight. [He doesn't elaborate more, not eager to get into the details, the endless days waiting at the hospital, watching her fade away slowly, forgetting...]
[And normally, he wouldn't even be talking about it at all, except he remembers what Yuuki said, off-hand at the time, but...] Yours are-- I mean, Yuuki said you went to live with her, for a time. So I just assumed.