Thanks for following up.
I had consultation with 3 different immigrant lawers. One advised me wait to meet RO, 2 of them encouraged me to process the sponsorship application ASAP. But none of them see any problems with the undeclared dependent. All of them believe it shouldn't be a problem while the relationship were truly girlfriend/boyfriend and not common-law.
About the RO, one of them advised me to wait until I meet RO, but I was being told to apply ASAP by the other 2.
The reason they gave me is: I've been living in Canada for more than 1 year, only 9 months left to meet 2 years, that's more than half time. Also my first daughter is attending school here, wife and other children are also living here at same roof. Plus, the sponsoring application is also a strong intention to stay in Canada, and I am unable to leave Canada while I sponsor someone. Moreover, I'm still a legal PR, and I have the right to sponsor family legally and lawfully.
They have processed many many sponsoring application without RO met like my case, they convinced IRCC may delay the process until they see I have the intention to meet RO or until I meet RO, but meeting RO or not isn't a fact for the sponsorship application rejection. One of the sign is IRCC does accept expired PR card on the application.
All of that makes sense to me, so I just go ahead and give it a try. At least the submission gave my wife/children temporary BC health insurance and the SOWP application gave them maintained status, so the whole family can be together, at least until I meet my RO on June 2026.