Screen sharing with an elderly parent

I occasionally need to help my dad with computer issues by having him share his screen with me. Sometimes it’s just OS related, but other times it’s to help with specific apps. It seems like the need for this remote operation has increased lately, and now it’s to the point where it would be extremely helpful if I could just control his computer remotely at any time without having to either have him invite me or have me request that he share his screen with me. I have a home network that allows me to remotely operate an iMac I have in my basement by simply clicking on a “screen sharing” button when I select that computer in the Finder from the list of volumes on my network. I’m wondering if I can setup my dad’s iMac in some way so that I have similar unfettered access to my dad’s computer, yet over the internet. Is this feasible? If so, would someone please share how that would be achieved? Gratitude in advance for your help. Much appreciated.