OK.. So, basically I have been playing on Sunset Valley, and I have reached week 6 or 7, and basically, Cornelia Goth and Gunther Goth had a divorce, and the elder Cornelia Goth moved in with Leighton Sekemoto and became his girlfriend. I don't know what happened to Gunther; he just disappeared. He didn't appear in any other households - I am presuming at some point he just died.
Now, we are left with Mortimer. I played with Bella Bachelor for a while, and made her marry one of my sims - they had a child called Ceril.
I looked at Bella's relationships, and Mortimer is one of her "Old Friends" and he became a fairy. I tried to invite him over about 20 times, but it said on all occasions.. "Oh, sorry, something just came up and I can't make it!".. I think this is rather suspicious.
I found myself, out of boredom, just moving around Sunset Valley and seeing what the other residents were up to, when I saw Mortimer walking down the street. He walked all the way to the pool next to the Roomies household. He started talking to someone else via his phone, then he had a little swim.. after he got out, he just disappeared... he literally just vanished. I went into Edit Town and looked at every single household... none of them had Mortimer in! Where has he gone? D: