Nguyen
Don't get the fess confused with filling the forms. See Well79's response.
You need to have a look at the forms and go through them carefully. In most cases, parents fill out one application form, as one parent is listed as the "principle applicant" and the other is listed as "dependent". So, it depends on your situation and I suspect that yours will be "principle applicant and dependent" kind of situation. But, you must read the instructions carefully. When you finally get the official invitation to send your application, CIC will send you a link to the application package and instructions. Read them carefully and fill out the forms as required.
As for the fees, they do not need to be paid separately, although you could also do that. You can pay for both of them at the same time and the total amount will show up on your official receipt. You will need to include that in your application package as well. For now, I suggest that you read through 2018 PGP instructions and fill out the forms just to familiarize yourself with CIC forms. I do not believe that there will be much changes in the application forms, but they may have some changes in the financial evaluation forms in 2019 PGP.