Hi @KritikaB - Yes, we completed form 47PA with my father as Primary applicant and my Mom as secondary applicant.
We included my mothers details under 'Part F - Details of partner' and Part H only listed their Children. Total cost payable on application in our case was $4,155 + $ 1,400 = $5,555 (plus the fees for credit card payment online) - Its a very long wait until we are required to pay the second instalment (Over 5 years or more) the website says they will send an Invoice.
Good luck with the application !