https://www.hotel-odessa.com/en/homepage-2/
We (just Dh and I) stayed here last week. It was very clean and we liked the neighborhood. It's an quick walk to the Montparnasse train station, Montparnasse tower (I recommend this!) and tons of restaurants. There is also a metro station right across the street.
We paid 170 euros, but prices might vary based on the type of room and the date.