Ah, I did the table wrong in my head. You're right. 2 genes, one from father one from mother, sibling A along the top, simbling A down the side. MM MF F

Ah, I did the table wrong in my head. You're right. 2 genes, one from father one from mother, sibling A along the top, simbling A down the side. MM MF FM FF MM 1 .5 .5 0 MF .5 1 0 .5 FM .5 0 1 .5 FF 0 .5 .5 1 (4+ .5 * 8 + 0)/16 = 8/16 = 1/2