Did your father have a will? If so, what did it say? Unless he specifically gave the copyrights to someone else, either in the will, or by arrangement before he died, the rights should remain within the family.
The answer depends, in the first instance, on whether your father assigned his rights or granted an exclusive license to the company that published the books. If you cannot find any contracts, you might want to contact the publishers and ask them for copies. If no rights were transferred, or if the rights reverted back to your father before he passed away, the manner in which the rights descended to the heirs can be complicated. Even if he transferred his copyrights to publishers, the Copyright Act allows authors or their heirs to terminate this transfers after a certain amount of time. Also, if the books are out of print the publishers may be willing to voluntarily transfer the rights back to the author's heirs. You should consult with a qualified attorney, preferably one with copyright experience.
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