Are there any opinions that either Abimelech and Sarah, or Pharaoh and Sarah, had children together? And if so, I would never suggest that would have any bearing on Yitzchak, since he's one of the avos and there is no question that Abraham was his father, but there is the concept that a drop from Shechem and a drop from Shimon combined to produce Shaul ha-Melech (two sources are given here Source text behind Rabbinic view on Dinah, Simeon, and Shaul noted in Jewish Encyclopedia), who was also a Jew, so I am wondering if there are any similar opinions here given the wording in Bereshis 20:2 that Abimelech "took Sarah," and in Bereshit 12:16 where it says Sarah was taken into Pharaoh's house, if possibly Abraham could be the pure father like Shimon but still also with an impure drop from Abimelech or Pharaoh, which maybe would have required the Akeida to separate from the pure, and which would fit with Yitzchak's middot being Gevurah? Or, the concept could fit with other similar concepts if it were the case. However to be clear, I know of no commentaries that suggest it is the case, but I think it's helpful to give some context for the question.
And then secondarily, I am also wondering could Sarah and Abimelech or Pharaoh have had children who were not Yitzchak, and who are not mentioned explicitly in Chumash but are explained in commentaries?