You must complete his year-of-death RMD. If his IRA is maintained as an inherited IRA for your benefit, his year-of-death RMD must be taken from the inherited IRA. If you have chosen to treat the inherited IRA as your own, you can take his year-of-death RMD from any of your IRAs.
If he died in 2025, you have until the end of 2026 to complete his 2025 RMD. However, it might be better to complete this distribution in 2025 since you can still file Married Filing Jointly for this year and perhaps have this income fall in a lower tax bracket than it would if taken next year. Taking it this year will also reduce the balance such that next year's RMD(s) will be lower than otherwise.
