I went to the store and bought two 12v relays with the 5 prongs at the bottom. And I was wondering, when I hook them up and lets say the car looses voltage and go below 12v, do the relays still maintain the 12v or do they decrease as well?

The relay can only output what comes in. If input voltage drops so will the output voltage. It's nothing more than an electrically controlled switch.

I went to the store and bought two 12v relays with the 5 prongs at the bottom. And I was wondering, when I hook them up and lets say the car looses voltage and go below 12v, do the relays still maintain the 12v or do they decrease as well?

Relays are electrically operated switches ...they are not storage devices. They take 12 volts to operate. If you have less than 12 volts in the cars electrical system you have less than 12 volts at the relays.

Ok thanks I figured that but I wasnt for sure or not.