> Has any one else noticed the way movies seem to come out in pairs ?
>
> Antz : A Bug's Life
> The Truman Show : Ed TV
> Deep Blue Sea : Lake Placid
>
> There are more but I can't remember them now

Dante's Peak and Volcano
The Abyss had a brother, too, but I don't remember what it was.

This is a common and well-known phenomenon. A certain idea gets hot in Hollywood, and people rush movies into production. Sometimes, though not always, it's the case where one movie goes into production and gets huge buzz, and some studio decides to rush a similar project into production to cash in on the hype. Volcano did this to cash in on Dante's Peak, and Antz did it to cash in on A Bug's Life -- in the latter case, the knock off actually beat the original to the theaters (by two whole months, even!).