Children generally have an optimum time frame for first language acquisition (up to around 5 years old, some research says it can be higher) and after this it is much harder to acquire language. They may struggle with their social interaction, understanding, vocabulary, formation of sentences, speech sounds etc.
One particular famous psychology case study on this is "Genie" where a child was kept in a locked room from about 20 months with limited interaction. She was only found and 'saved' from abuse when she was about 13 so massively missed out on language acquisition. Her language was very minimal. Have a look into that case, there will be many other cases too unfortunately I'm sure.