Snipped by me.
I don't think it's excessive. They're in a foreign country, maybe their family just want to check in to make sure they're OK. Every family is different. I see some grown daughters who appear joined at the hip with their mothers, calling them their best friend, texting or calling multiple times a day. (To me, that's excessive) Others have no contact at all. They last spoke with the other triplet around the new year - not at all odd to wish your siblings a happy new year. It seems she wasn't in phone contact with them again before they disappeared, which was about a week it seems. The mother last spoke to them on the Saturday prior I believe, so seems like it wasn't a daily thing. Not sure about the brother. Maybe they were all in a group chat of some sort online, maybe they followed each other on socials, maybe not. I live in the same city as my mother (who's on her own now) and I call once a week, sometimes more. It really comes down to the individual family, and their circumstances. In this instance, they can't visit each other often and being that they live in different countries, checking in and hearing their voices is a reasonable thing to do IMHO.