of the righteous

This nominal adjective can be stated as an adjective. AT: "of the righteous people" (See: rc://en/ta/man/translate/figs-nominaladj)

in the days of our fathers

"during the time of our forefathers"

"we would not have joined with them"

Here "blood" refers to life. To shed blood means to kill. AT: "killing" or "murdering" (See: rc://en/ta/man/translate/figs-metonymy)

Here "sons" means "descendants."