I'm working on a historical fiction novel based on a real family's journey as captives marching hundreds of miles midwinter up to Canada. I only have one MC and throughout the book she will mostly be surrounded by her immediate family (2 parents, 4 siblings), and many friends. Discounting other minor characters, there are already too many to keep track of in every event, interaction, scene, discussion, etc. And I find myself having to name every character and what they're doing at the start of every scene, because if I don't, the MC looks like she's forgotten about her family, or is just plain careless about what happens to them (which is furthest from the truth). How do I consistently show the MC's close connection, reliance, and concern for her family -six other characters- without bringing them up repetitively? The stakes in the story are high, so the whereabouts of her family are important, but not something I want to excessively catalog throughout the book.
Include things when they are important to the story. Readers aren't going to think your MC has forgotten her family and friends if they're not constantly mentioned. Establish their importance and then let them serve roles that are important to the story. The story needs to be what's compelling and the focus. Otherwise you're juggling a million different stories and the focus will likely be off more than it's on. I'm a fan of well-populated stories, but tame those characters and use them appropriately. Remember it's a story and not a play-by-play of every characters life. Even character-driven fiction tends to have a strong focus on the MC and not everyone they know the same. This won't lower the stakes of the story. Sometimes less is more. There whereabouts can be important, but if you keep coming back to that, it will likely lose some of the weight and importance you want it to have.
I agree with @deadrats , sometimes to many can bog you down, and less can be more. So you will have to find a way to incorporate them in ways that don't detract them from the story, or: Make it quick, and they won't feel a thing.
Ask yourself what or to whom you'd have paid attention throughout such a track. There most likely will be a few who you are closely tied to. Others you will care about, but the needs of your immediate family transcend that caring, because, put bluntly, it's your family or the others. You simply can't ensure everyone makes it. Sidenote: Read up on the death-marches of Jews and/or Sudetendeutsche in the build-up to WWII. Their marches probably will compare to what your MC experiences. Your readers will emphasize as long as you show from time to time that your MC cares about others than her immediate family too. Maybe to give them a kind word of encouragement when she sees them struggling. It's not all heroics. Or maybe I should say that heroics can sometimes be expressed in very simple ways.
It's easy to forget about the twelve different friends and family members a story's protagonist has and not worry about what's going on with them, it's not easy to focus on the protagonist and their journey when their twelve different friends and family members keep showing up all the time. As the previous other commenters have said, you can show your MCs attitudes towards their friends and family without dragging the lot of them into the mix, but instead just including a few that are closest to the MC and/or most involved in their own right in the main plot.