A relay circuit is shown first.
S1 and S2 are momentary contacts.
R1 and R2 are normally open relay contacts.
R1 and R2 are also the coils of said relays.
Press S1 first, then S2 second or Press S1 and S2 simultaneously and both relays latch. If you press S2 first and S1 second, nothing happens, except that S1 is latched, now the circuit is waiting for S2 to be pressed again.
Interrupting power resets the relays.
A dual D-flop version is shown below.
Begs the question of what happens if the rising edge of S2 is absolutely coincident with the rising edge of S1? As it is, depending on the logic family, S1 would have to preceed the rising edge of S2 by a few nsec.