When our family was growing, my husband and I decided that we didn't want our house to be like a hotel. Each person having their own room and not interacting with each other until meal time. I have seen this with other families and didn't like it. So in order to foster family togetherness we put the 2 girls together in a room and the TV in the family room. The girls can watch videos in thier room but no TV.
If you think back to your childhood, most houses were built with 3 rooms. One for the parents, a boy's room and a girl's room. That was considered spacious because prior to that, it was just a one room house for most families for centuries prior. So sharing space has been the custom for most of civilization. This recent notion that kids need thier own room is an American thing just as taking daily baths. So if you don't have space for each to have their own room don't fret.
I actually have space for my girls to have their own room but we chose to have them share a room. They will only have this time in childhood to live together and learn to share and cooperate together. It isn't total bliss all the time between them especailly when it is time to clean the room. They fuss over who left the sock on the floor and who should have to pick it up. But when I walk past their room and they are in their giggling, reading to each other and telling stories about their day, I can't help but smile. They have thier inside jokes. Where saying one word and make them both laugh and leave me wondering what the heck is so funny!!
If I am out shopping and I want to purchase an item for one of the girls but she isn't on the shopping trip, I can ask the other because they know each other's styles. So think about how you invison your family dynamics will be in the future and if having thier own space works for you and them, so be it.
I am pro sharing a room. Good luck in making your decision!!