Shade pedigrees proportionally in R

I have a pedigree where bred individuals are coming from two different sites.

I would like to shade the pedigree such that the proportion of each symbol shaded is equal to the proportion of genes coming from site 1.

library(pedigree)

id <- c(1:8)
father <- c(NA, NA, 1, NA, 4, NA, 6, 6)
mother <- c(NA, NA, 2, NA, 3, NA, 5, 5)
sex <- c('male', 'female', 'female', 'male', 'female', 'male', 'male', 'female')
site <- c(1, 1, NA, 2, NA, 2, NA, NA)
df <- data.frame(id, father, mother, sex, site)

pedAll <- pedigree(id = df$id, dadid = df$father, momid = df$mother, sex = df$sex) 
plot(pedAll)

Here is the figure I would like to achieve given the sample code:

Here is the figure I would like to achieve given the sample code:

I have not been able to find any documentation among the various pedigree libraries which specify a way to proportionally shade symbols.

Any insights on how to automate this shading are much appreciated!

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