Their acting is pretty evenly matched for sure.

Well, I'm with y&rfan here...and with you.

I think JM and AH are both very low key, low emotion, go with the flow types. This shows up in their acting (even when it should be otherwise). So they feel very natural--like siblings--when they're together. Also, since LML, there was a scripted backstory of Nick teasing Victoria (those made up memories...most notably when Victoria read Nick's letter to her at his funeral). Some of that playfulness is just behind the eyes with these two.

I like them as siblings. Indeed, I probably like AH most when she is in one-on-one scenes with JM...they feel natural and the level of emotion is right.

That's the thing. When they match these actors with the right materials (AH-JM in low key sibling scenes; Hayley Erin as pouty brat; I'd even argue Muhney is far better in softer scenes with Sharon Case and Eileen Davidson), we still get decent results. The sole exception for me yesterday was Adrienne Frantz and Jeanne Cooper. I wasn't understanding why they were like "family" anymore. We haven't had enough ongoing connection between the two of them, and it felt forced to me on both sides. Cooper seemed to be a lot more delighted in her boardroom scenes than in her GCAC scene.

I like them as siblings.

They aren't even in the same universe as Heather & Josh.