British Nationality which form to use?

[ss32]

Hello,
Hope everyone is fine and well. First of all I would like to thank the experts as their advice has helped me and many other people who access this forum. Thank you for your help and support.

Secondly today I was looking to apply for british citizenship of my cousin. He is 11 years old now. He came to the UK in January 2017 on a child dependent visa when he was four years old. His father was a British Citizen. His father got british citizenship by naturalisation after his birth. My cousin was born abroad out of uk. After three years in January 2020 he got ILR. Now we want to apply for his british citizenship but I am not sure that which form should we use to apply for his citizenship? Shall I use the MN1 form or any other form? He wasn't born in uk and his father wasn't a british national at the time of his birth. I'll be grateful if someone can help me with this query. I'll be waiting for your response.
Thanks
Best regards

[alterhase58]

MN1 for registration of minors under 18, the only form for this purpose.