You're right, they weren't his kids, but that didn't stop the "The Clone Wars Character Guide" from calling those children half-human half-Twi'lek.
That source/book is not The Clone Wars. It falls into lower level of canon just like the rest of the similar stuff. So in the end it is one source that contradicts other sources that previously established impossibility of human-twilek interbreeding.
Not to mention this Star Wars: The Clone Wars Character Encyclopedia states things that are actually wrong (some of them are mentioned on its site on Wookieepedia). It is clear that this was just another low priority source to milk some additional money.