Did Reuven have only two sons when the brothers met Yosef in Egypt?

May this post be in merit of our soldiers, a swift return of the hostages and a speedy recovery for Dror Yisrael ben Rut Miriam (דרור ישראל בן רות מרים).

I noticed something interesting while reading last week's parasha. After Yosef claims that his brothers came to Egypt to spy on the land, the brothers are forced to leave behind Shimon and go back home to bring Binyamin. Yaakov, naturally, is against this idea. Reuven says the following (Beresheet 42:37):

"וַיֹּאמֶר רְאוּבֵן אֶל אָבִיו לֵאמֹר אֶת שְׁנֵי בָנַי תָּמִית אִם לֹא אֲבִיאֶנּוּ אֵלֶיךָ תְּנָה אֹתוֹ עַל יָדִי וַאֲנִי אֲשִׁיבֶנּוּ אֵלֶיךָ"

"Then Reuben said to his father, “You may kill my two sons if I do not bring him back to you. Put him in my care, and I will return him to you.”"

What's interesting here that in this week's parasha it says that Reuven had four sons (and that was the case for later mentions of Reuven's sons). But Reuven doesn't say "You may kill two of my sons" or "my two eldest/youngest sons". He just says "my two sons", as though he only has two sons.

As is well-known, there are many issues with the way in which the 70 descendants of Yaakov were counted in our parasha: There are actually only 69 people named, why weren't the twin sisters of the tribes counted, why was Dina counted, and the chronology: If only 20 years had passed from the start of Vayeshev until the end of Miketz, how was Yehudah already a grandfather through Peretz? Various commentators have explained the discrepancies in various manners. Some have suggested that certain individuals hadn't been born yet and were only included later. It seems therefore possible that Reuven's two younger sons still weren't born when they came down to Egypt.

Food for thought.