Tank size

[Redeye79]

Is. A 36"x18x18. Big. Enough. For. Two baby. Valid

 

[qdude46]

It's bit enough for one. Unless they are pygmies which should be in glass, all other chameleons shouldn't be housed together unless they are young and will be separated before 4 months or so. What kind do you have, your post is quite vague. Welcome to the forums though!

 

[Psychobunny]

When you say tank, do you mean a glass terrarium?

If so, I recommend you get them a screen cage.

It's very difficult to keep good air flow in a glass box!!
With some inventive rigging, it can be done, but why go through the trouble
and extra expense when you can get a small screen cage way cheaper??!!

If they are under 4 months old, you can keep them together, unless one is
being more aggressive then the other.

The size you mentioned is fine for babies.