There is very little written in scripture about Abraham’s brother Haran. From the three verses in Genesis, we know that Haran had at least three children: Lot, who was adopted by Abraham and became his traveling companion; Milcah who later became Nahor’s wife; and Iscah. We also know that Haran was born and died in the land of his birth, Ur of the Chaldeans, and that he died before his father Terah died, in his presence.
Rashi speculates that Iscah is actually Sarai in part due to some similarity in the meanings of both names, because Sarai was beautiful to look at, and the name Iscah means ‘to gaze’ as people would ‘gaze at her beauty’. Josephus also lists Sarai as the daughter of Haran, but there are known errors in Josephus’ writings. I find it odd the way the text handles Iscah and Sarai, as the text introduces Milcah specifically as being the daughter of Haran (v. 29) whereas Sarai is not introduced in that manner even though it would have made the text flow easier; also later in Genesis 20:12 Abraham explains to Pharaoh that Sarai is his half-sister on his fathers side, though this isn’t mentioned in the original genealogy (is Abraham lying again here?); If Sarai was Haran’s daughter, that would make her Abraham’s niece, not his sister. I believe the jury is still out on whether Iscah was Sarai. There is a great document on it here.
Although not in the text, my other studies have turned up information about Haran which was oral tradition at some point so I decided to share. According to Josephus in his Antiquities, book 1 chapter 5.6, Haran was well-known in Ur of the Chaldeans (which appears to be a pagan city); in fact there was a monument of him there. And, according to Josephus, Terah his father hated Chaldea (the founder of the city perhaps?) on account of his mourning for his dead son. Why? We do not know. In response, Terah packed up the family and moved to a city called Haran in Mesopotamia.
According to Rashi, Haran may not have had a great relationship with his father. He notes that the phrase “died in his presence” may signify that Haran died, in some way, because of Terah. There is apparently a whole backstory to Terah, which again, is not in scripture at all, but rather in the tradition. We do know from Joshua 24:2 that Terah “served other gods” but traditionally, Terah both made and sold idols as well, which at some point Abraham destroyed. Nimrod became involved, and Haran got caught in the middle. Having to choose between Abraham and Nimrod, Haran ultimately was killed by being thrown into a fire.
There is no obvious moral lesson in all this, just an example of how tradition can differ from the scriptures, or add more details from time to time.