Yes, casement windows can be replaced with double hung windows. There are a number of considerations when switching window types, including height and width of the opening, load bearing, and how the window is attached, or mulled, to the window next to it.
Another option for side-by-side casement windows is a gliding window. Gliding windows can appear like double hungs in a wide space and they increase the glass area by eliminating the wood frame in the center. Even picture windows can be effective, depending on whether you open your windows or not. Creative solutions to window replacement can save you money and give you a more desirable outcome.
Depending on your location, the best way to explore creative window replacement options is to work with a window design consultant. You are under no obligation to purchase from them, however, you will benefit from spending a few hours with an expert like this who can give you great ideas, with the knowledge and experience of what works.
You will get your questions answered, a quote for the project you design, and plenty of workable ideas and solutions. Appointments like this are free and well worth the time and effort. Although there is plenty of information on the Internet, having an expert in your home is far more valuable in this case.