You MUST be Permanent resident or Citizen of Canada in order to sponsor for your parents.
As such, any income that you earned BEFORE you become Permanent residents will not count
You have just become Permanent resident in 2017 so your Tax return for 2017 count.
However, you MUST meet 3 consecutive years income requirement immediate before your application, which mean, you will be eligible to sponsor your parents in 2020 if your total income for 2017 + 2018 + 2019 meet the requirement each and every year respectively. This income requirement is updated every year on the IRCC website
https://www.canada.ca/en/immigration-refugees-citizenship/services/application/application-forms-guides/guide-5772-application-sponsor-parents-grandparents.html
The above Guide will also show you how to calculate your family size and, how to determine if your siblings are eligible or not.
But to cut short, if you meet the following criteria:
1/ You are single: Not married and/or No common law partner
2/ You have no kids of your own
3/ All of your siblings are NOT under 22 years old
4/ All of your siblings are NOT dependent on your parents
---> Your family size which is used to determine the income requirement is 3. But let's say, you are married in 2019 and have a baby in 2020, your family size would then be 5.
Hope this helps