It's not wrong to use now but it's typically used (aside from when someone prefers to be referred to as such, of course) to talk about multiple people OR a singular person whose gender you don't know/is ambiguous, for instance a hypothetical person. If you know the person's gender/preferred pronouns then you would refer to them using their preferred pronouns, usually he/him or she/her.
If you were talking about your mom, you'd probably refer to her as "her," not "them."