Dad Won't Seek Help. How do I help him?

My brother took his life three, almost four, months ago. My dad found him. Now he won't seek help, and I'm not sure what to do or how much to push.

For context, my dad has been semi-retired for the last few years. He's kind of leaned into a routine-less existence since then, and just before this happened, he started taking care of his health a bit better. But it's always been an uphill battle. He'd rather watch movies and hide away than interact with the world.

My dad has had a pretty traumatic life leading up to this. He has childhood trauma, and my mom had a severe eating disorder that left all of us in worse shape following the recovery. He's never gone to therapy and never really dealt with these stressors. It's apparent in the way he talks about any of it, if he talks about any of it. He only ever relives - he never works through things.

Now, it's like he's given up. I call him, and he says he isn't sleeping regularly. He barely leaves the house. He won't take a walk. Today, he told me he doesn't want to try to get a routine and is perfectly fine just spending his time watching movies, taking naps, and sitting with the dogs. His mom was the same way. Severely traumatized and essentially agoraphobic. My cousin told me he only eats ice cream and chips, and that he stopped cleaning.

I don't know what to do. I've asked him to go to grief counseling, and he always gives me an excuse. Or says he just hasn't gotten around to it yet. I don't believe he's going ever going to seek help on his own. I think he's just putting it off, and, frankly, I think he's lying to me about what he's even doing day to day. I think he's comfortable letting himself waste away, just like his mom did. I don't know if I can stop it, but I don't think I can accept it either.

Has anyone else dealt with this? What did you do when your loved ones didn't want to get better after a suicide in the family? My plan is to get all of the materials together to connect him with a bereavement group and a PTSD therapist, but how do you approach these conversations?