With Skyteam Elite (Plus) we get some benefits such as Preferred Seating. Looks like airlines handle it differently when flying with a companion.
For example Delta seems to extend Elite benefits for companions, so that I can also select e.g. exit row seats for them for free, while on KLM/AF I would have to pay for them.
What other SkyTeam airlines have you flown with a companion? Did the benefits get extended to them? Could you select preferred seats for them and did they get any other benefits such as priority lines etc?