I researched this a long time ago (as in just after we entered the GV programme) because I was concerned about what would happen to the family if the primary died along the way. This was the information provided by SEF at the time wrt family reunification under Art 98(1) of Lei 23/2007:
“Two years after the issue of the first residence permit and in as much as there are family ties or, regardless the mentioned deadline, whenever the holder of the right of family reunification has underage children living in Portugal, the members of the family have the right to an autonomous permit, valid for three years, and renewable, under the amendment introduced to article 75 of the Aliens Act, by article 192 of Act n.º 75-B/2020, of 31 december. The first residence permit granted to the spouse under the family reunification is autonomous whenever he/she is married for more than five years with the resident – valid for two years, renewable for three, under the amendment introduced to article 75 of the Aliens Act, by article 192 of Act n.º 75-B/2020, of 31 December.”
This aligns with what the European Commission’s Immigration Portal currently has on family reunification in Portugal:
Family member in Portugal - Migration and Home Affairs (updated 1 April 2025)
I don’t know if anything has changed with the latest round of PT law reforms, but its worth knowing that European Council Directive 2003/86/EC on the right to family reunification sets a limit of no more than 5 years of residence as a family member after which member states must allow for autonomous residence (Art 15).