Yes, it is very much possible. When you do good Karma, you increase your chances of being born in a happy destination. When you do bad Karma, you increase your chances of being born in a place of misery.
The likelihood of people being born together or meeting in future lives increases if you do good deeds together. Also, they should be in tune with each other:
"If both husband & wife want to see one another not only in the present life but also in the life to come, they should be in tune [with each other] in conviction, in tune in virtue, in tune in generosity, and in tune in discernment. Then they will see one another not only in the present life but also in the life to come." - Samajivina Sutta
Yes, it is possible for a stream enterer to know that he no longer has certain fetters.
