It sounds like you're trying to convey sarcastic humor. The reason "tell me about it" works for talking about yourself is because it is sarcastic. The meaning is "That is so obvious that I already know it," but the words are essentially saying, "I didn't know that. Tell me about it." The humor lies in saying the opposite of what you mean.
You can carry that principal of "saying the opposite" to a situation about other people if there is something obvious (or generally understood) that be contradicted. Perhaps while the child is making noise, the mother is holding her phone to one ear and plugging her other ear with her finger so she can hear the person she's speaking to.
Observer A says, "That kid sure is loud."
Observer B sees the mother plugging her ear, and he replies, "Yeah? His mother doesn't seem to have any idea."
It's sarcastic because the observers can see that the mother knows that the child is noisy. If the mother wasn't trying to block the noise, the sarcasm wouldn't be effective.
You can still convey sarcasm if the mother isn't there or isn't showing awareness, as long as you have something that is obvious or understood from the circumstances. For instance, the child is noisy every day at school. The teachers have sent notes home to the mother, and finally the mother has been asked to come to a meeting at the school to talk with the principal about her disruptive child.
Teacher A says, "Wow, that kid sure is loud."
Teacher B replies, "You'd think his mother would have heard about it by now."
Since the school has told the mother about the child's noise many times, the teachers know that the mother has heard about the issue, even if she hasn't done something about it.