Connecting two power supplies and preventing reverse feeding either
I'm using two power source and because of "even with 0.0001 V difference, they are going to fry each other when you connected them in parallel" rule.


This is not a rule. There are many cases when power supplies can be paralleled. These include battery, mains DC PSUs and AC transformers. 

Many power supplies including batteries, simple mains rectifiers and transformers have internal resistance or, for AC, impedance. The effect of this is that the voltage will droop to some extent with increasing current draw. This in turn means that if one supply is taking the bulk of the load that it's output voltage will drop and the supplies will tend towards balance.



Figure 1. When sharing a load an exact match of power sources is not required. Image source: Loddon Valley Lions Club.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 2. Equivalent circuit of Figure 1. Each horse's internal resistance tends to balance the load sharing.

If your power supplies are tightly regulated but to different output voltages then you may have problems as the one with the higher output voltage setpoint will try to power the load and may backfeed into the second supply. Unfortunately there isn't enough information in your question to address this.