עַד־שׁ֨וּב אַף־אָחִ֜יךָ מִמְּךָ֗ וְשָׁכַח֙ אֵ֣ת אֲשֶׁר־עָשִׂ֣יתָ לּ֔וֹ וְשָׁלַחְתִּ֖י וּלְקַחְתִּ֣יךָ מִשָּׁ֑ם לָמָ֥ה אֶשְׁכַּ֛ל גַּם־שְׁנֵיכֶ֖ם י֥וֹם אֶחָֽד׃
네 형의 분노가 풀려 네가 자기에게 행한 것을 잊어버리거든 내가 곧 보내어 너를 거기서 불러오리라 어찌 하루에 너희 둘을 잃으랴
Rashi on Genesis
למה אשכל means WHY SHOULD I BE BEREAVED משניכם OF BOTH OF YOU? — The one who buries his children is termed שכול bereaved: so we find in the case of Jacob (43:14), “If I am to be bereaved (שכלתי) let me be bereaved”.
Rashbam on Genesis
גם שניכם, if he will kill you he in turn will be executed by the blood avengers.
Or HaChaim on Genesis
גם שניכם יום אחד. "both of you on the same day." Rebeccah said to Jacob: "even assuming that Esau would die in an act of self defense by you or an act of revenge by a relative of yours this would not give me any satisfaction at all." Rebeccah's concern was only for the life of Jacob; she did not care about Esau at all.