Welcome......You can crate the litte one because 12 weeks is young having it roam at night. I wouldn't crate the older one as he was there first. You might create another problem. In the day dont crate let the get use to each other. Munson reminds me of mine just loves anyone, anything, jumps, licks till you get fed up. Good characters. It's the little one Sugar, you will have to say no to.12 weeks they are old enough to start discipline. Snapping is not good as it leads to bites later on.