Illegitimacy isn’t the issue. Fewer teenagers having children is a good thing, and entirely different from marital status. Having a child as a teenager, or being the child of teenage parents, is associated with worse medical and life outcomes regardless of whether they’re married. The current increase in illegitimate children is entirely due to women in their 20s or older; the poorer outcome for children of adult single mothers is predominantly due to lower income, not to the absence of a father or loose morals or any of the stuff conservatives like to rant about. Also see discussion of this topic here.
There is no such thing as an ‘illegitimate child’. It is the parents union that isn’t legit.
My two bits.
Well, yeah, but for convenience sake, I don’t know how to really say that. Writing out a child whose parents aren’t married takes a lot longer–no judgment was intended.
Why don’t we just go back to calling them bastards? That wouldn’t offend anybody, right. 
It wasn’t terribly unreasonable to assume it was her kid. It *was *terribly unreasonable to assume it was her business to comment. If I’d been your SIL’s friend, I’d have said “Don’t you think your boss wants my money anyway? And while we’re being all curious, don’t you think your mama should have raised you better?”