Pull from so many different existing characters that it makes a new one. If there’s an actor that you really love, watch a bunch of their stuff and then combine the different characters they’ve played. That way, when you’re writing, you can picture that actor and it will make it easier to not blend characters. Another thing you can do is download sims 4 create a sim demo and make the characters on there. It will save to your origin account and then you can look back at their personalities and the way you initially pictured them.