Re: Two hedges in one cage...
No, it is absolutely not possible to house them together. Spiff *is* sexually mature. If the girl is old enough to be living with you away from mom, she's old enough to get pregnant. It is very likely they would fight, and then you would have to have two of everything after anyways. The girl would get pregnant so young that her growth would be stunted and it would be very dangerous for her to be pregnant/giving birth.
Ferret cages can work but they are difficult to modify to be safe. You'll have to enclose every level and ramp, and make sure the floors are covered if they are wire. Some ferret cage work well, some don't. Also keep in mind a lot of hedgies want nothing to do with a second floor. Hedgies need horizontal space, not vertical.