They lived under Communist rule and did not know anything about praying and fasting; do they have to make it up?

No File Exists
Check below answers in case you are looking for other related questions:
Is the person who prays Friday prayer only not a kaafir?
Is it permissible to pray on behalf of someone who does not pray?

No File Exists
Related Answers:
He committed adultery with a woman and she married someone else, and the adulterer wants to marry her
A Christian woman is close to becoming Muslim and is married to a (Muslim) man who does not pray. What is the ruling on her marriage?
Condition of saying Bismillaah in order for meat to be halaal
Is the person who prays Friday prayer only not a kaafir?
Is it permissible to pray on behalf of someone who does not pray?

Recommended answers for you:
He committed zina with her and she got pregnant; can he marry her while she is pregnant or should she abort he foetus?
Does Ludo come under the heading of dice games which are prohibited?
If she sees some brownish discharge after her period ends, should she pray and fast?
How can he make up for missed prayers?
Dreams and dream interpretation