If I have a brother, we both gain half our genes from each parent, however statistically we should have about 1/2 our genes in common, as we don’t get exactly the same genes from each parent (assuming we aren’t identical twins). My question is how strong is the bias towards our genes being exactly 50% commonality. My impression is considering the number of genes being selected by a process that seems to be strongly random would result in the the bias being very high. Am I correct? If I am, how strongly biased are later generation towards maintaining this bias?
IIRC, the genome is large enough, and the number of crossing over events high enough, to ensure that siblings will share very close to 50% of their variable genetic material.
ETA: I did find a numerical answer to this question a few years ago; I think the standard deviation was 0.1% or so, but I can’t find the source right now.