Well wasn't expecting to learn more about that incident from the Mamool Ja society quest line finisher.
It looks as tho Zereel Ja didn't order the attempted drowning of Wuk Lamat when she was a toddler. I'm going to assume that it was blessed siblings related as even though female Hrothgar are still rare they're not as rare as a successful attempt at a blessed sibling. He didn't even know that the girl survived or that she had grown up to be Wuk Lamat. To me him feeling relieved at learning from Wuk Lamat's father that she did is genuine. Same for knowing how lucky he is that Wuk Lamat is the way she is when it comes to forgiveness. It was a really nice let's burry the hatchet this time kind of moment.