In Parshas Toldos, aside from Yaakov and Eisav, where are the second set of twins mentioned?
Rashi says that Tamar also had twins.
Yitzchak tells Yaakov to marry "one of the daughters of Lavan your uncle" (Gen. 28:2). According to Seder Olam Rabbah (ch. 2), Leah and Rachel were twins.
In the first posuk, it says "Avraham holid es Yitzchak" to teach us that Hashem made Yitzchak look exactly like Avraham to stop the scoffers from saying that Yitzchak was really conceived from Avimelech.
I do not know if this is correct, however I will try.
The Posuk says "Shnei Goyim B'Vitnaich" Rashi says it says Gayim, not Goyim which alludes to Rabbi & Antoninus. There is a well known story about how Antoninus saved Rabbi's life when they were both infants, by Antoninus's mother and Rabbi's mother switching them around in order that the Romans should not see that rabbi was circumcised. I do not know if they were born the same day or if they were a few days apart, and they were definitely not twins, however their lifetime friendship is well documented, and maybe this is what the question is alluding to.