Get it together

We keep inconstant company
To care and share alike
The only things you won’t divide:
Your food, your pets, your bike.
Her lipstick’s on the headboard
His fags are on the floor
But somehow through domestic life
One tenet does endure
You always put the seat down
To keep me on my toes
So I must guess the pronoun
From the drink, the scent, the clothes