I share a DNA match with a male person of 152cM coming up as a 3rd cousin. I also share a match with his half brother but much Lower at 45cM. These two share the same father but different mothers. I’ve since learnt that I am the Great Grand son of their Grand father. ( Grand father fathered my Grandmother). These two males are of the same generation , share same father and share same Grand father ( my Great Grand father )
Why is one so far removed from than the other ?