biérén别人 and rénjiā人家 can both means ‘others’ but the latter has a broader use.
First, the people that rénjiā人家 refers to are normally known by both speaker and listener, so is usually translated as ‘them’, for example,
1) 张和王在睡觉，别打扰人家
Zhāng hé Wáng zài shuìjiào， bié dǎrǎo rénjiā
Zhang and Wang are sleep don’t bother them
‘Zhang and Wang are sleeping, don’t bother them.’
Second, rénjiā人家 can also refer to one person rather than a group of people, for example,
2)张在睡觉，别打扰人家
Zhāng zài shuìjiào， bié dǎrǎo rénjiā
Zhang is sleep don’t bother them
‘Zhang is sleeping, don’t bother them.’
Third, rénjiā人家 can also refer to the speaker himself/herself, for example,
快回家，人家害怕
Kuài huíjiā， rénjiā hàipà
Immediately go home I afraid
‘Go home as soon as possible, I am afraid.’
