Dear Farhad Alizadeh ,

Look the link, maybe useful.

Article Cryptic Distant Relatives Are Common in Both Isolated and Co...

Regards,

Shafagat

You can refer this link for better understanding : https://isogg.org/wiki/Autosomal_DNA_statistics

Hope this will help you in you work.

Check https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3317976/

https://journals.plos.org/plosone/article/figures?id=10.1371/journal.pone.0034267

Also check http://si.biostat.washington.edu/sites/default/files/modules/FGBruceSection5_0.pdf

https://www.researchgate.net/figure/Schematic-of-IBD-half-inference-method-IBD-half-segments-were-inferred-from-unphased_fig1_224053185

Also look at this thesis

http://www2.unb.ca/~owen/zeeshan_thesis.pdf