Add a comma after home.
Change the dash after standing in to a comma.
Add a comma after charge and another after work.
In this example, as is supposed to mean due to the fact, more or less, but the meaning is… blurry. I’d recommend changing it to because or since.
The three orphaned siblings were left to fend for themselves. With no family, no home, and only the clothes they were standing in, one of them was going to have to take charge, but since they were all too young to work, it was going to be a challenge.