The RMD for the beneficiary IRA must be satisfied from the beneficiary IRA and the RMD for your own IRA must be satisfied from your own IRA. The beneficiary IRA is still actually your father's IRA but now maintained for your benefit as beneficiary, so nothing about it can be combined with your own IRA(s).
Since your father died before 2020 (and it's reasonable to assume that he died after his required beginning date for RMDs), your father's age is not relevant to determining your RMD for the beneficiary IRA. Your life-expectancy factor for the beneficiary RMD is determined from Table 1, the Single Life Expectancy table and your age in 2019 (age 69), reduced by 1 for each subsequent year. For 2025, the result is 13.6, meaning that the 12/31/24 balance in the beneficiary IRA is to be divided by 13.6 to determine the RMD that must be taken from the beneficiary IRA.
For your own IRA, if you do not have a spouse who is more than 10 years younger, your life-expectancy factor comes from Table 3, the Uniform Lifetime table, based on your age in 2025 (age 75). That factor is 24.6, which you'll divide into the 12/31/24 balance in your own IRA(s) to determine the RMD that must be taken from your own IRA(s).
