Most of the time, family rooms provide bedding that sleeps at least 2 adults and 2 children, allowing a family of 4 to comfortably share one room.
Family-friendly hotels often also have additional rollaway beds and infant beds available (at a surcharge). If young children share existing bedding, there's usually no extra charge So, depending if these are available at the hotel of your choice, it could be possible for more than 4 people to share a family room.
On Expedia, you will find room details listed for each room, such as number of beds and types of beds, so you can make the right choice to book for your family.