We can intercede for generations.

Scripture:
“But they and our fathers dealt proudly, and hardened their necks, and hearkened not to thy commandments, And refused to obey, neither were mindful of thy wonders that thou didst among them; but hardened their necks, and in their rebellion appointed a captain to return to their bondage: but thou art a God ready to pardon, gracious and merciful, slow to anger, and of great kindness, and forsookest them not.

Yet thou in thy manifold mercies forsookest them not in the wilderness: the pillar of the cloud departed not from them by day, to lead them in the way; neither the pillar of fire by night, to shew them light, and the way wherein they should go.

Therefore thou deliveredst them into the hand of their enemies, who vexed them: and in the time of their trouble, when they cried unto thee, thou heardest them from heaven; and according to thy manifold mercies thou gavest them saviours, who saved them out of the hand of their enemies.

Nevertheless for thy great mercies' sake thou didst not utterly consume them, nor forsake them; for thou art a gracious and merciful God.

Behold, we are servants this day, and for the land that thou gavest unto our fathers to eat the fruit thereof and the good thereof, behold, we are servants in it:

And because of all this we make a sure covenant, and write it; and our princes, Levites, and priests, seal unto it.”
‭‭Nehemiah‬ ‭9:16-17, 19, 27, 31, 36, 38 (KJV)

Application:
All of us have ancestors who have strayed from God. Indeed, those who follow us may say the same thing about us. But there's something that we can do that perhaps very few people even think about:
Intercede. 
We can right now pray a prayer of remembrance of God's mercies and His promises to forgive and bless us, the children of past generations. Each of us has the authority to intercede and call upon God to forgive the sins of our forefathers and bless all of us as descendants who know Him and agree to follow Him and only Him. That's something unheard of. We need not be prophets or preachers. Just doers of God's Word. 

Prayer:
Father, not only have we strayed, so have our ancestors. We remember Your kindness to withhold punishment that we all deserve. We pray that You will forgive us and continue to bless us, helping us to stay on the right Way to righteousness. Amen. ​