IPhone 4S not auto connecting to home Wi-Fi?

Out of the 4 iPhones in the house hold one doesn't connect automatically connect to home Wi-Fi I have to manually put in password it wouldn't bother me so much if it wasn't my personal phone and suggestions on how to fix this through my phone I have no options to remember network through my phone but it does remember networks of places I have been and connects automatically

TURN Wi-Fi ON IN SETTUNGS.

Reset your Iphone. Clear your Profile form the Iphone. Set up as a new member to the phone. & then check if it connect automatically.

You can any time get back your profile.back by adding the Itunes user name & password & it can revert all your changes.