When to use "他的太太" and when "他太太"? I've read the two different sentences, of which one uses "他的太太" and the other uses "他太太". How can I tell the difference between the two?

For example, in the following sentence:


现在他想他的太太。
现在他想他太太。


Which is the correct sentence? And why?
When you want to express possessive relations concerning family members or relatives, you don't need 的. 

我妈妈，你爸爸，她男朋友，我们家老大, etc.

I have done some searches with different expressions with and without 的, and I see that this rule is not applied consistently. 

EDIT: There are ambiguous cases, e.g. 你们孩子 could mean "You children" or "Your children" (with plural you in both cases, of course). In such cases 你们的孩子 would make it clear what the speaker means.