K.H.
My two boys, ages 5 and 8 share a room and have since the younger was about 6 weeks old. They do go through phases where they play more, and goof off before bed. It is frustrating, but I have started to think that it is actually a great thing that they get along so well and love each other so much. Sometimes I will just sit outside and listen to their conversations...it is precious. I love that they are such good friends. I do get that it is frustrating...my boys are old enough that they eventually stop and just go to sleep on their own, but I do remember when it was more work for me. What I sometimes do is put them down to bed a little earlier, like 30 minutes early, and let them play all they want. Then, bedtime. Good luck!
There are still nights where I am downstairs and hear them at 9:30 or 10:00 (way past bedtime) giggling, and I have to go up and tell them to be quiet...
Good luck!!