Way too little sex, please help

How can my boyfriend and I improve our sex life? I think our biggest problem (since we got into a relationship over two years ago) has been lack of privacy. I still live with my parents because rent is just way too expensive. The house is old (creaky floors, thin walls, etc.) and my room is above the living room, so unless everybody is asleep, they will hear it CLEARLY. My parents also work from home so they are always in that living room, as it doubles as an office. By the time everyone is asleep, one of us is usually too tired.

The situation is similar at his place, he lives with his brother (long story). His room is attached to the living room and doesn’t have a proper door, it's more like a thick shower curtain. So not sound proof at all. His brother is depressed and spends his time on the sofa next to this curtain door. We are not noisy at all, but hearing his brother watching stupid sitcoms and making lunch is just a mood killer.

We have gotten to the point where we have gotten used to very little sex, and even though we have been trying to improve our sex life, it is just not in our system anymore and we forget. We both hate it. We probably have sex twice a month, maybe less. For a couple of two years in their twenties I think that's dramatic.

Any tips? Please help!