Is it considered haraam not to give married sisters their share of the deceased father's debts that were collected for the family, and what is the way to repent from that?

Debts owed to the deceased are included in the estate and are to be divided among all heirs according to their legal shares.

The sisters must be given their share of the past monies, and an apology should be offered to them for the delay. If they willingly agree to waive their right, then the obligation is absolved.