Hissing, swatting is all normal. Right? My 15 wk male kitten is very territorial, ?

I swear it seems like he is not letting Serenity eat or use the litter box. When I get home she is hungry and ready to the litterbox. She cries in the middle of the night. When I take her to the food and litterbox. She is fine after she eats and uses the box. Is this too going subside after getting familiar?