I can see the family resemblance! :-)
This is looking pretty solid already. The caps especially are actually really good; this is a font that should have smallcaps. The "m" and "C" are a bit wide. The bar of the "K" stands out a bit too much. The "Q" has too much serif in it. I'd make the "T" a bit narrower. The bottom of the "U" is malformed.
For 10 point, it's pretty light, and a bit loose. In fact I think it would be useful to match the serif in color and fit. If we assume the serif to have stabilized, the sans should be a bit tighter and slightly darker.
I predict this sister-and-brother team is gonna be famous, in
a starlet kinda way I mean, not like the Osmonds or anything. :-)
hhp