I want to try to give an element of response, following a couple of texts. The good actions of good persons are what they leave on the earth. If the consequence of the actions of these persons is a good think, it its kapara. Gemara in BB 4a said:
He (Baba Ben Buta) replied (to Herod who killed wises): As you have extinguished the light of the world, [for so the Rabbis are called] as it is written, For the commandment is a light and the Torah a lamp, go now and attend to the light of the world [which is the Temple, of which] it is written, And all the nations become enlightened by it.
Some report that Baba B`Buta answered him thus: As you have blinded the eye of the world, [for so the Rabbis are called] as it is written, if it be done unwittingly by the eyes of the congregation, go now and attend to the eye of the world, [which is the Temple] as it is written, I will profane my sanctuary, the pride o your power, the delight of your eyes.
Rabbenu Yona reported a statement (congruent to Gemara in Sanhedrin 52b (perhaps was it an other Girsa than our Gemara) Shaare Teshuva III, 218:
ונאמר (משלי כט) תועבת צדיקים איש עול. ונאמר (שם ה) יראת ה' שנאת רע. ואמרו רשע בן צדיק מותר לקרותו רשע בן רשע. צדיק בן רשע מותר לקרותו צדיק בן צדיק.
The wise said that it is allowed to call a Tsadik Ben Rasha Tsadik Ben Tsadik.
Following our Girsa this statement can be infered obviously.
I know that you are not offspring of these persons, but, according to the comment of Rashi about "Ele Toldot Noach Noach", the offspring of Tsadikim are them Maassim Tovim, we can infer: A man who helped Jew to not be killed have some percentage in the Maassim Tovim of this family. And each Mitsva you make adds a credit, and help him to be called Tsadik in such a manner.
A salved B, and B made Maassim Tovim, the MT are as a wish of A, so A has a Tsadik part in his personality. This tsadik part was potential and became effective through B.
I am afraid that this answer seems strange, but for me it's true. The more you make mitsvot and Kiddush Hashem, the more you give them Kappara.