We have done affected sib pair studies for many years with moderate success as we already described five years ago. Professor John Edwards brought to my attention the “sib similiarity problem“, that is still not widely known. ASP studies are based on “the premise that a set of ASPs will share more than the expected proportion of alleles at a disease-susceptibility locus with the implication that these were the sole cause for excess sharing”. This is not necessarily true and may be one reason of the failure of ASP studies. More or less by chance, I found that that the observation of 1 discordant sib in ASP families be an extremely powerful. “Being sane in an insane world” e.g. being healthy while having most of the risk alleles and all the environment risk that made the sibs ill. Yea, yea.