being the dad, and you could end up with this kind of result, especially if a recent ancestor or two weren’t really your ancestors.

Unreported adoption is another possibility, as mentioned elsewhere in the thread.

One young guy in my ward (not the one I mentioned previously) did a DNA test and found out his paternal grandfather couldn’t possibly be his grandfather. So he and his dad questioned the grandfather about it, and he finally confessed on his death bed that he wasn’t really the biological father of his son, a fact he and his wife had always hidden.

In another family that used to be in our ward, the wife had an affair and became pregnant. She and her husband decided to stay together and he agreed to raise the son as if he were his own. They moved across the country and are still together. They have 6 kids now, and the one looks very different from the other 5, but I don’t think the parents plan on ever telling him the truth, if they can avoid it. He’ll be in for a big surprise if he does a DNA test later in life, and only a handful of people know who his real dad is.