Was the earth populated by Noah’s sons and daughters and their children married each other?

Answer:

Only eight people were saved during the Flood (II Peter 3:20). "So Noah, with his sons, his wife, and his sons' wives, went into the ark because of the waters of the flood" (Genesis 7:7). Noah's three sons were Shem, Ham, and Japheth. With the wives of each, that makes eight people. Noah didn't have any daughters. It was his daughters-in-law who joined them on the ark.

From the three couples, the world was repopulated -- Noah and his wife did not have any more children. "So God blessed Noah and his sons, and said to them: "Be fruitful and multiply, and fill the earth" (Genesis 9:1). Genesis 10 and 11 give the genealogy of the initial generations after the flood.