Indeed I was. It’s part of the ‘how South Scadrial acquired Feruchemy theory.’
340, to be exact.
Dox indicates that Kell was something of a womanizer before Mare (or, at least, was known for attracting female trouble). However, the above theory would have him fathering a child/children out of duty, not desire.
My current headcannon is that Kell has a crush on Khriss, much to everyone’s amusement (except Kell, who dislikes being teased, and Khriss, who is unaware).
If I’d asked more specifically I would have received a RAFO.
Note that Brandon usually clarifies if he’s using the word ‘child’ in a non-standard fashion and he wasn’t even slightly cagey about this, so I’m fairly certain this is a straight yes. (In both of your examples he adds an asterisk, while he gave me a simple yes - no caveats.)
Returned cannot have children in the normal manner either, btw. Certain things need to be done. And CS’ are definitively NOT Spren, thanks to an earlier question I’d asked. They don’t have as much innate Investiture, so likely could not procreate the way Spren do.