Welcome to Flyertalk Unsub!
I'd say it would be natural at check in at least. Priority security is usually printed on the BP and thoroughly checked. (Airlines pay extra for each pax going through prio sec). So that is not likely to work.
For boarding, AY is not well known for enforcing their rules, but the brarding group is also very visible on the BP.
One idea would be to go to J checkin together and just ask if they are able to put you in the same boarding group and perhaps even get prio sec printed on both BPs.