How to convince labmate to graduate? Graduating, in a 2 person research group? I work in a small research group, there are 2 graduate students. 
My advisor is fairly new, and I'm not sure when his tenure date is actually set for. Not necessary info, but pertinent.)
The other graduate student got here a year before me and worked with our professor a lot to set up the lab and has contributed to all of my works. He started in the group with 2 M.S. degrees from different universities. 
I'll have the necessary attributes in order to graduate 2 years from now, my 5th year, but I'm not sure how I can leave a group at the same time if my other labmate will be also leaving that year...
I can't imagine staying for a 6th year for no reason. Only because my boss doesn't have enough funding/ likes keeping the group small.
Yes a lot can change in 2 years, but if my labmate isn't apply for jobs for next Fall/Spring, then how am I supposed to apply for jobs next year...There's no way we could leave at the same time and leave my advisor with only 1 graduate student (if he were to hire a new one NY then).
How do I push my labmate to apply for jobs? He's already got some great publications. He's totally ready to go.
I'm part worried that he's not ready to push his way out. I'm not sure how to get out without this turning into a difficult situation.
How many graduate students your adviser attracts at any given time to his or her lab isn't your responsibility. Your responsibility is to yourself and your career. If you think it is time to graduate and if you think you have sufficient material to defend your thesis, then it is time to graduate.

Leave the details of how to run the lab after your departure to your adviser. It might make sense to discuss your hopes and plans to graduate at a particular time with your adviser well in advance (it's always a good idea to communicate!) so that she can plan accordingly. But, this planning is her job, not yours, and it shouldn't be a factor in your considerations.