If the hydrants are equidistant from the Tee - then the flow should be the same - what ever the water pressure / volume.

If the hydrants are in parallel from the same pipe - it depends upon the volume of water and the pipe size (pressure drop).

I'm not a plumber - there must be charts.

Easiest solution is to keep the 2 hydrants off one line but put in a flow restriction before the one nearest the pump. An adustable valve would avoid having to do any calculation. Otherwise, I would narrow the first pipe to 3/4" at the end (cut the water volume in 1/2).

Even if running to a Tee, if you want to split the water evenly, going down a pipe size is common. Reduces maximum flow if only one hydrant open, but if your intent is both always open with even flow then either 1.25" to split with 1" after or 1" to split with 3/4" after. Which is ideal depends on flow rate. Using too big a pipe encourages all to flow to nearest hydrant. Too small and tends to restrict all flow. Note that material matters. 1" PVC has bigger inside dimensions than 1" of other pipe materials like CPVC or PEX.
Flow in Pipe sizes roughly: 1" is double 3/4", 3/4" is double 1/2". This is because flow is proportional to surface area which goes with the square of radius of pipe