1994 RangerTrail Tandem

Need some help, my brother bought a 1994 Ranger w/Tandem axle trailer w/brakes. He tells me he has a 4-prong connector and a seperate 2-wire connector off the trailer, he connected the 4-prong and said he can't back-up an incline to his garage. I assume the 2-wire connector is the power and ground for the brake solenoid, is this correct? If so, is there a way to wire both the 4 & 2 prong connectors into 7-prong connector so he only has to connect 1 thing to his truck?

He will be towing with a F-150 that has a tow pkg so he already has a 4 & 7 prong connector on the truck.

Yes, the additional 2 prong plug is the hot and ground for the brakes. I would assume that he could take the hot wire and, along with the 4 prongs from the trailer, connect them to a 5 prong plug and then use a 5-7 prong connector to his truck. I would think the ground for the trailer would also function for the brakes.