I suggest you do not house them together.

"can" they be houses together without an problems... maybe, but why would you risk it?

I've known/seen/ read about individuals housing milks and even kings together without problems. it's great that it works for them, but i can't see myself risking any of my snakes for it. Plus the vast majority of keepers recognise it as a very bad idea.
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1.1 Argentine Boas
1.1 Dumerils Boas
1.1 Black Milk Snakes
2.3 California King Snakes
1.1 Nelsons Milk Snakes
2.2 Corn Snakes