The game everybody is playing right now is, "what's the catch?".
Because no way the guy Emily assures us(insert angry
Defenestrator.for.traitor noises) is our father can be the father of Alexis and Layla, right?
So everyone is free to have their theories, such as...
They have a different biological father(supported by the fact that neither girl uses the name Navarro), but Santiago is Adriana's husband.
He's not Adriana's husband, Alexis just made a weird joke(doesn't go well with the fact that Santiago is buying what Alexis likes for breakfest).
He is their father and Emily is the one that is lying/miscalculated.