Date Night

Immediate Family: Blind Date
Family Gossip: Note how the Bruce Willis' appearance makes the Date Night stars look rather tidy by comparison.

How To Train Your Dragon

Immediate Family: E.T.
Distant Relative: Sistine Chapel Creation of Man painting
Family Gossip: Note how Dragon references the fingers and the moon from E.T.

Babies

Immediate Family: Babel, Havoc, Bee Season
Family Gossip: Fellow poster fan Matt alerted me to this one, and pointed out the Babel/Havoc similarity. Thanks Matt!

Star Trek

Immediate Family: Kids, Queen's Hot Space CD
Family Gossip: Kids got the order of colors right (red/blue/green/yellow). Star Trek got it wrong.

Inception

Immediate Family: Dark Knight Teaser, Watchmen Teaser
Distant Relative: Escape From New York

Lightning Thief Teaser Poster

Distant Relative: Alien

The Wolfman

Immediate Family: Traffic, Jack Kirby's "floating heads" comic book layouts
Distant Relatives: Platoon, Freejack
Family Gossip: Del Toro and Hopkins were both floating heads on other posters!