Well, we know that the dad (whose name I’ve forgotten, and I don’t feel inclined to bother to look it up), was “playing away” in the last series. Lowri had referred to her cousin Gwenno in the last series, but we hadn’t seen her. However, I think she did bump into Gwenno’s husband one day in the last series, with “another woman”. He made some excuse I think, but it was obvious that something was “going on”.
At the time, Lowri had just started, or was just contemplating starting, her affair with Philip. However, you could see that the sight of someone else having an affair (and the disapproval it led to - from “The K’s” if I remember correctly - they got to hear about it), gave her pause for thought.