Moshe Rabbeinu’s children weren’t at matan torah when Hashem gave the torah to Benei Yisrael. How is this possible? Why weren’t they there, and how could they miss such a special event? Please, if you could give provide this question with a sufficient answer that would be helpful & with a source, I would really appreciate it. This question derives from Parshat Yitro, Chapter 18 pasuk 5 and 6 (I heard from someone that answer comes from Ramban that Yitro came after matan torah).
The Gemara (Zevachim 116a) cites two opinions concerning whether Yisro came after Matan Torah or before Matan Torah. Ramban, in fact, prefers the opinion that Yisro came before Matan Torah, although he also mentions several proofs that are brought for the other opinion.
According to the opinion that he came after Sinai, several commentaries discuss the question of the presence of Moshe’s children at Sinai. Chizkuni (Shemos 18:27) writes that they were indeed not present at Sinai, and writes that this is the reason for which further to their actual coming with Yisro, they are not mentioned by the Torah. Rav Berel Pavarsky writes (Bad Kodesh) that they were not at Sinai because only those who were present in Egypt could merit being at Sinai, however, they joined the nation later, as geirim (converts), just as a non-Jew could join the nation. Maharil Diskin (al ha-Torah) writes a novel approach, explaining that in fact, Moshe sent for his children, so that they should be present at Sinai, but promised Yisro that they would be returned to Midyan after the event. When Yisro brought them to Moshe, they came for the second time. With this he explains the wording of the verse, achar shilucheha, which implies that Tzippora was sent twice, not once.