R package sped, which does multigene descent probabilities (Thompson, 1983, doi:10.1098/rspb.1983.0072) and special cases thereof (Thompson, 1986, doi:10.1002/zoo.1430050210) including kinship coefficients. But does much more: probabilities of any set of genes descending from any other set of genes.
To install, use your favorite method of installing from github, for example
library("remotes")
install_github("https://github.com/cjgeyer/sped", subdir = "package/sped")
Now on CRAN https://cran.r-project.org/package=sped
So better install for most useRs is
install.packages("sped")