家 means the family or the place the family lives, so we say 回家 (going home), 我家 (my home).
To me, as a native speaker, 家里 seems nearly the same as 家里人. Like I would say 我得跟家里说一声这事 (I have to tell my family about this), or 我家里都知道了 (My family has known), or 我家里人很支持我 (My family is very supportive to me). You see here 家里 and 家里人 both mean the people in a family.
I have to mention that I am not 100% sure about the nuance between 家里 and 家里人, with respect to the meaning "a group of family members". Of course when meaning something else, you should be able to distinguish them, like you should say 在家里 (at home) rather than 在家里人。