A big welcome to our forum! I can see it has taken courage and thought for you to write your post. I can see that Jas and Bugsbunny have both made some very helpful points in their replies to your post.
I also congratulate you on your strong family ties and values which shine out of your post. I am one of six kids, we are lucky to be a functional family with zero feuds, and it is so sad to hear of a family when members have a falling out and don't speak to each other.
This blimmin Covid thing has a lot to answer for doesn't it! The media are loving it with their very dark updates, the worse the news, the better it seems to them. I wonder how the media will cope when it improves? My wife now refuses to watch the mainstream news bulletins because of their inflationary negativity.
Living alone can be awesome and a great way for you to get to know yourself. I can see you choose to do this and are not a recluse as you love and miss the social contact and stimulation of your workmates. Don't we all?
A couple of very simple things to try (if you haven't already) are a Zoom mini get together with some friends, Have a wine and nibbles handy and you'll be the envy of the group! The second thing is a very simple facetime call with friends and family. If kids are present, they can 'animate' you face as you talk and other stupid but funny things.
In regards to moving in with you father and sister, I agree with Jas and Bugsbunny and can't see any issues with that at all. Awesome idea! You may need a letter from one of your Counsellors.
Over the next day or so I intend create a thread on our forum about how our Olympic athletes are coping with sudden quarantine, right on the heels of being in the adoring public eye. The common thread is they like to have a schedule and keep busy every single day. Some of them just don't have the time to get depressed or feel anxious!
So I do hope this has helped a little bit - please stay in touch and let me know how you are going. We are here for you.