Frequently Asked Questions - Green Card through Parents

LPR petition for son

It will be faster for her to petition and she can do so as soon as she wants. I would suggest she should apply when she moves to USA. If you wish, you can also start a petition for your brother. He can wait in more than one category.

GC petition for a 21 year old

Sure. The fact that he is in Canada is not an impediment.

GC through mother ....

As far as I know your PD cannot be reused because you lost it through becoming ineligible for the visa category.

Father wants to sponsor me

Review Form I-130. You cannot stay in USA while or just because the case is pending, unless you have some visa/status that allows you to stay.

Dual Intent Visas and Filing green Card in Multiple Categories Simultaneously

See clip from Attorney Rajiv S. Khanna's conference call video that addresses this question. 

https://youtu.be/R4-_pic6TzY?t=103

FAQ Transcript