My #1 is 21 months now and has not started talking. Still uses baby language like mum-mum (eat), though she's able to call papa, name out some animals but many elders are telling me that she's should start to talk by this age. Any idea how do I get her to express herself the correct way? I tried letting her watch videos on YouTube but doesn't help.

Children develop at their own pace. Elderly relatives tend to compare babies or with you as a child. Although I respect and value their opinions, somehow, they just give me stress :-) It's good that your lo is able to say some words, which goes to show that she's developing well. But feel speech may not be expected until 3 years of age. Some may be younger than that and same may be older, specially if you are a multilingual family. You can encourage your lo to talk more by talking to her more. Engaging her in conversations and read to her stories and be interactive during the story telling. Hope this helps.