How to clone a record in a custom entity & the related child records on click of a custom button 'Clone Record' on the form?

Hi,

I am using Dynamic CRM 2015 On-Premise. 

I want to clone a record in a custom entity & the related child records on click of a custom button 'Clone Record' on the form.

Please provide some example on how to clone a record in a custom entity & the related child records on click of a custom button 'Clone Record' on the form.

Thanks in advance.