s it okay to make up your own surnames?

Yes it's perfectly fine cuz my friend did it 2 :) good luck

Sure, it's your story and your imagination. If it makes sense with the character and blends in with the story, or just..something inside you tells you to use it, then go right on ahead :)


There's a saying I always have when it comes to writing;
"Trust the gut"
If there's any idea that suddenly strikes you and you from within that it's a good one, trust yourself. And go for it :)
Think about it if you wish to, but I'd suggest that you listen to yourself when you have some type if intuition like this. ^^