removing an unwanted SIM charcter

It has been a while since I've played, but what do you know what the settings are in your game? I recall options regarding "fill houses" and choosing the amount of sims to spawn in your game. I'd go check on those areas first. Your house may have been empty for so long, the game just automatically generated a couple of sims to live in it.

As for how to get them out of it, when in manage worlds, it shows you the map. Click on the desired house, it should show info on the sims living there on the left bottom corner as well as options like to play as them, visit them and other things. Look for "Manage Households" and in the world you have the house built in. They should show up as one of the households. Click on them to edit. Their info should appear with options to edit, move, switch between households or delete completely. So, if you want, you can move them to some empty house, an empty lot, anywhere marked residential. You can even dump them onto some other family if there is enough room... or you can completely kick them out of your game by deleting them.

PS. If my instructions or not clear ('cause I'm sort of bad at that...) just look up "How to move Family in Sims 4" in the search bar and you'll likely find others who have supplied those who have asked similar questions far better instruction than me. ^__^0