When you have problems in the family, do you let your children know about it or you hide it from them?

my sister has a 5 year old and a 10 year old. the 5 year old is too young to understand about family issues, but the elder one is now very perceptive. so my sister has started talking to her about certain issues that are there in the family, as she knows her daughter will be able to sense it on her own. so, instead of letting her find out from somewhere and feel bad, she talks to her herself.