I'm sorry for your loss.
I don't think I would expect anyone other than very immediate family (like your brother) to invite me for Christmas, and you know why he hasn't. Godparents and friends of your parents, no.
I agree it would have been nice for your close friends to ask what you were doing for Christmas, it's a pretty normal conversation this time of year, and to offer to have you when you responded that you will be on your own. But have you asked anyone what their plans are either? Have you got into any of these conversations?
Anyway, Christmas on your own isn't all bad, just the once. I did it a couple of years ago when circumstances worked out that way. I'd broken up with ex that year, my family weren't able to have me for various reasons. I did have a friend offer but I turned it down as she had a big family Christmas planned at hers and I didn't want to intrude, plus it was the first time she'd done it and she was already freaking out about it. I got a pity invitation from a work colleague, which was kindly meant, but rather humiliating so I refused nicely. I fibbed to everyone. Told family I was going to friends. Told friends I was going to family. Enjoyed quite a nice day sitting on my bed in my PJs, picking at yummy food, watching all the rubbish TV I wanted and reading my new book without feeling guilty. As a one-off, it was fine.
But only as a one -off. The next year I was a bit more proactive about it all.
If you are on your own this year, make the most of it. Enjoy a peaceful, relaxing Christmas day doing exactly what you want. Raise a glass to your parents. Next year, start inviting others round to yours for Christmas. Sometimes you have to take the lead.