Unless Uther was the reason why they couldn't have children. I still think at this point we should take Igraine being barren at face value but if there does turn out to be a twist and she did have a child before, it still could be down to him.

I agree that Uther might have felt some resentment if Igraine had a child with someone else, but his love for her is so strong that I imagine he'd feel more resentment towards the child than Igraine. Besides whose to say that she was even with Uther at the time? Like I said 'Igraine-barren-face-value' but I'm just saying anything is possible.

The bottom line for me is wanting to know why Morgause's birth was so significant and why everyone wanted Uther to believe that she had died at birth?