I suppose I should have expected it, with the manager looking so youthful, but I thought the little sister is only in high school herself. In fact, it's actually more plausible that she's living in the brother's house if she's a uni student now. They move out as a matter of course, unlike high school kids. After all, there often isn't even a choice but to move (their new specialised college/university/other school is often far away), and being young adults, they want to move out and get independent.
A landline phone, huh. Those are getting exceptionally rare where I live. Already twenty or more years ago phone companies, turned primarily carriers/ISPs, began to push people to voluntarily get rid of their landline deals. They even marketed mobile phones that were made to look like landline phones to older customers who wanted to stick to their trusty old phone. There were also GSM modems being marketed that allowed an old phone to be connected to the digital mobile network (sound quality was typically dreadful, though). Nowadays there isn't much left of the telephone lines anyway. The copper got recycled and company expenses reduced.