Oh yes, I do mean that they were both adopted. It’s just that the birth mother (in my opinion) was impregnated by two different men.
Although to be perfectly honest, if you looked at my older son and my younger son, someone might say the same thing about them. They look nothing alike, but both have the same father and mother. It’s more that one has so very many of the recessive genes in both families, and the other has many of the dominant genes. They have a few similarities, though, in body build and in their chins. That’s about it.