Can I use a single wire and run two jumpers to two gcfi outlets and on the other side run two wires off the single wire to two gcfi circuit breakers?
NO WAY!!!!
If I understand you correctly, you want to run 2 15A circuits over one cable. You can't do that. (There are certain exceptions involving a 3-wire cable, but I assume you are describing an ordinary 2-wire (plus ground) cable.) Depending on how you wire up those two circuits, you would either end up overloading the wires (30A on wires designed for 15A) or just outright zapping everything by ending up with 240V when you want 120V.
Following up a bit more based on comments:
Assuming that each device specified by the manufacturer only actually uses 7.5A, that would be too much for a single 15A circuit (therefore requiring two separate circuits) but small enough (15A is less than the 16A continuous limit for a 20A circuit) to fit on a 20A circuit, and therefore on 12 AWG wire.
However, aside from being a violation of the manufacturer's instructions, which is a big no-no on permanently wired devices, there is a potentially fatal flaw:
If you slam two circuits into one, you have no way to control which circuit actually carries the load! It might go 50/50 (as planned) but it might not. In addition, if one of those wires comes out, you now have all 15A of load going over a single circuit. While technically OK in the short-term, that is exactly what the manufacturer is trying to avoid by having you use two circuits in the first place. In addition, if there are any startup loads then there could be real honest-to-goodness overloads involved as well.
But wait, there's more! This will probably not actually work anyway because not only do you want to nominally split the circuits 50/50 for load purposes, you must split the loads consistently on hot and neutral. That just ain't gonna happen. Which means you may end up with frequent GFCI trips. Which inevitably leads to &quot;who needs this GFCI stuff anyway&quot;. Which leads to taking out the GFCI and replacing with regular breakers &quot;just for a little while to test things&quot;. Which of course becomes permanent. Which results in serious (possibly fatal) problems when there actually is a ground fault in a bathtub.
NO @#()$@&amp;#$)!@@# WAY!