[cypher]

That is a huge difference, siblings can be quite different but that does look as though Francisco may be hogging the food, how do you know they both eat the same amount, it's hard to tell with hams as they usually take food away to eat & stash.
Is Stephano more active than Francisco? Again it can be hard to tell I know as they tend to be most active when we sleep.
Keep a close eye on them if you upgrade the cage, the stress of the move or the extra space could be enough to cause them to fall out.