My boyfriend and I, very much in love, were talking and gushing over each other on IM as usual. All good, right? But then he said "Oh one second my mother is prowling about, gotta make sure she's not listening for me." Obviously that makes sense because she probably doesn't want him on the computer. Right? Okay. But then I talked to his brother, also online, and he said "Well mother is fast asleep." Why would he just do that?

I think you need to stop asking brother, and either trust him or not.
Next how late at night was this

It was at about 11 o clock PM.