Only one of the 30 versions of translations that I've checked translates this verse according to the Hebrew text. In the text of the Torah it is written that the name of the one was Gershom and the name of the one was Eliezer. The Torah doesn't say one of them and the other one, or the first and the second, but the one and the one, in Hebrew ha-echad – האחד. Wouldn't it be more logical to say one and the other?

 When the Torah says something out of the ordinary, it does due to a very specific purpose i.e to teach us something important. Then, what can we learn from this?

I think that the Eternal is teaching us a very important lesson regarding Moshe's relationship with his sons. When the first one was born, he was an only child and all the love and attention from both parents were directed to him. Then, when the next one was born, it is logical that the love and attention from the parents were divided between both of them. But by mentioning that Eliezer was the one, even if he was the second child, HaShem teaches us that he was treated as if he was the only one. Both sons were considered unique.

This teaches us that parents can't have preferences regarding love and attention to their children. All of them must be treated as if they were the only ones and preferences or comparisons must not be made between them. It isn't (emotionally) healthy to compare one's children. Each one has to be treated differently according to his or her own particular traits and uniqueness.

 On the other hand, it teaches us that for the Eternal, each boy and girl born in this world is unique. As the love of the parents doesn't diminish for the first son when the second is born, the love of the Eternal doesn't diminish when more children are born in this world. He loves each one as if we were the only ones.

 This also teaches us that if there would have been only one person in the world and he or she had sinned, the Eternal would have laid the burden of his/her sin upon Yeshua so he would have died only for him/her. Thus, we can understand Paul's message that says: "...who loved me and gave himself for me." (Gal. 2:20b ESV) The Eternal's love through Yeshua is very personal.