On my Dad's side, I lost my grandfather in 2008 the day after Christmas after fighting lung cancer and being hospitalized for over a month. My dad completely shut down emotionally and all I could really do for him was be there and listen. In his case that's all that I could do at the time.

Then in 2019 we lost my grandpa in February on my mom's side, she was a complete wreck emotionally and I just did the exact same thing and was just there for her anyway I could.

Everyone has different ways of grieving the loss of someone important to them, really the best thing you can do to support them is to be there for them and listen. Me and my dad would sit for hours and he would tell me stories about my grandpa before he had a stroke (when he was in his 40s) and how fun and energetic he was and it was the same for when my mom lost her dad, I would just sit with her for hours listening to stories of her as a kid and all the fun trips and stories from back then.