What's Going on in Exodus?

Moses and the Israelites are close to Sinai in Midian. Jethro comes out to meet them with Moses' wife and two sons. They had been staying apparently with Joseph while Moses was busy at work. Now, earlier in chapter 4, if you remember, we hear of just one son, Gershom. But now we see he has a second son, Eligazer. And again, as I said, perhaps this is an extension or a continuation of Exodus power at this moment.