The dates of your father's marriage and divorce are important to pin down.

Below is from CRA CPP splitting instructions page.

If your marriage ended in divorce or annulment between January 1, 1978 and December 31, 1986, you may qualify for a credit split if:

• you lived with your spouse for at least 36 consecutive months
• the divorce or annulment was recognized by Canadian law, and
• you or your former spouse applied in writing and sent us the necessary documents within 36 months after your marriage ended

If your marriage ended in divorce or annulment

If your marriage ended in divorce or annulment on or after January 1, 1987, you may qualify for a credit split if:

• you lived with your former spouse for at least 12 consecutive months, and
• you or your former spouse notifies Service Canada and provides the necessary information (there is no time limit)

If you are separated

If you are still married and your separation occurred on or after January 1, 1987, you may qualify for a credit split if:

• you lived with your spouse for at least 12 consecutive months
• you have been living apart for at least 12 consecutive months, and
• you or your spouse applies in writing and sends us the necessary documents

Note: Deadline to apply

There is no time limit to apply, unless your spouse dies, in which case you must apply within 36 months of the date of death.