That bit of information is, of course, not included in the cartoon! Although we only have the writer’s word for it that the chap spends time on his phone – he might just look at it from time to time, and she spends every second on it. We Shall Never Know!
Oh, I dunno…maybe he’s just a nice guy who is fed up with how his girlfriend treats her, and sees that Tiff is quite insecure. He has to run after her as he won’t get to see her now without Stef hanging onto him.
If the chap is driven mad by his wife’s sister’s phone use then why on earth invite her to spend a week with them? Especially as it’s their holiday home.
No, it’s the lady from panel 1 who works at the nursery.