that resulted from the genotypes of many surrogate parents. Often the cause could be a genotyping error in the proband. Nevertheless, genotype correction was not attempted. Note that probands were processed one at a time, but the updated information for one proband was not applied to the phasing of the others until the next step/iteration, and thus the ordering of the probands had no impact on the results. After each proband had been processed, Step 3 was then repeated, and the successive iterations brought in information contributed by surrogate relatives with Erdös distance 3 and higher. Round 1 was completed when the results of the iterations stabilized. At Step 1 of Round 2, a review was performed to identify surrogate parents who were part of multiple incompatibilities (Supplementary Methods). They were then removed from the surrogate parent list, i.e. even genotypes of theirs that did not lead to incompatibilities would no longer be used. Steps 2 and 3 were then repeated.
