I used the form and got this reply ... I guess just cross fingers as it sounds like they can't commit to scheduling them together.
To Whom it Concerns:
The NVC processes immigrant visa petitions as they are received from U.S. Citizenship and Immigration Services (USCIS). While we do attempt to process and schedule related cases together, we cannot guarantee that this will happen. Each case processes differently, and some may take longer to process than others.
Regards,
Albert | Inquiry Management
Department of State CA/VO/DO/NVC
LDRM | Lockwood Hills | Contractor
DOS - National Visa Center