Hannah Brown, South Australian Health & Medical Research Institute
Semi-identical or sesquizygotic twins occur when two sperm fertilise one egg. A boy and a girl in Brisbane are only the second set of semi-identical twins known in the world.
Are they twins? Are they identical? Are they natural? Which one is older? These are some of the all-too-familiar, somewhat invasive and highly personal questions posed by well-intentioned strangers to…