any two full siblings will, on average, share 50% of their DNA. they each inherited 50% of each parent's DNA, but between siblings it will not be the same 50%.
This means that if the parents have enough offspring, their full genomes would be represented in the DNA of their brood.
My question is, how does one model the probabilistic propagation of the parents' genes? my guess is:
proportion of genome passed on = 1 - 0.5^n
where n is the number of offspring.
so with 4 kids 93.75% of each parent's genome would be passed on. of course sorting out what came from who would be a whole can of worms.
During meiosis each pair of chromosomes in the parent cell will undergo chromosomal crossover so that the chromosome passed to the child is not an exact copy of one of the two parent chromosomes but a new hybrid. So while I think you are right that there is a point at which you can say probably 100% has been passed on, it is based on the smallest chromosome fragment that is created during meiosis and not based on the smallest overall chromosome size.