Summoned creatures & readied attack.

[GM Chyro]

If 2 people ready an attack and someone summons a monster in a square they both threaten, would they get to make the attack?

[Chess Pwn]

Well if their ready was an opponent being within reach or something like that then yes.
If their ready was for an opponent to charge them or something like that, then no.

[GM Chyro]

The monster is summoned onto a square adjacent to both of them.
It'd be nifty if the readied would go off, otherwise the npc would taste 3 attacks if they can't execute those hits.

[Magda Luckbender]

It depends entirely on exactly which action they readied, and on what was the trigger conditions for the readied action. A readied action must be of the form, "I ready action X with trigger condition Y", or something similar.

[GM Chyro]

Hm, then the reason of 1st enemy that comes within striking range applies. I like it.