activate a relay with two esp8266 -12e pins
That is not a good idea.

Isolating the relay from the IO pin is not just about the current limit of an IO pin, it's also about preventing back-EMF spikes from the relay coil(s) from damaging the delicate internals of the chip.

Instead you must at least use a transistor and a back-EMF protecting diode.

However - if you did want to theoretically have two pins safely controlled to provide double the current (though I stress again, do not do this for driving a relay), it is possible.

But it's not straight forward.

It's not possible on the ESP8266 to use port manipulation to make two pins change state at the same time. However it is possible to go via a third state that makes it safe.

Note: this will only be "safe" for IO pins that do not do strange things at bootup, and many of the pins on the ESP8266 do strange things.

IO pins actually have three states, not two: 


High
Low
High Impedance


The latter is the state the pin is in when in INPUT mode. And we can use that to our advantage.

When in High Impedance mode it's like the pin is disconnected.  So we could:


Make sure both pins are in INPUT mode
Switch one pin to OUTPUT and set it to the desired state
Switch it back to INPUT mode (keeping the desired state latched)
Switch the other pin to OUTPUT and set it to the desired state
Set the first pin back to OUTPUT mode again.


This can be slightly compressed as we don't really need to set both pins to INPUT at the start, only one.  So here's some code that might do it:

void digitalDoubleWrite(int pina, int pinb, bool level) {
    pinMode(pina, INPUT);
    pinMode(pinb, OUTPUT);
    digitalWrite(pinb, level);
    pinMode(pinb, INPUT);
    pinMode(pina, OUTPUT);
    digitalWrite(pina, level);
    pinMode(pinb, OUTPUT);
}


You might ask why we'd want to switch to OUTPUT just to latch a level into the pin. Well, that's because of a quirk of the Arduino API. A historical artefact that is lingering in there to this day:


digitalWrite() on a pin set to INPUT mode was used to turn the internal pullup resistor on and off


It's actually how the AVR's IO ports control the pullup resistors internally, and that has most often been copied in software for other chips to maintain backward compatibility with old code. So as a result we have to switch to OUTPUT mode so that the API code knows that we mean to set the output latch state and not the pullup resistor state.