What is the second attribute for Val'Holryn? It's not listed in the core. It say Charisma which is for all Val, but doesn't list another attribute.

under val racial traits val'Holryn count as the family they get their powers from

Also what do the do for bloodline powers?

So the choose a family then during character creation.

Yup. You are Holryn with X family's powers, and only their powers.

Oh, let me provide a more detailed response:

the val'Holryn family has a lot of interesting things going on with it, when you play a val'Holryn character you select another family, for you powers to copy, and for all intents and purposes, you are (mechanically) part of that family with all benefits and restrictions and character creation choices that go along with that.

now story wise.. they have some interesting things related to them and milandir, and the spawn of val'Sosi.

No one knows for sure what's really up with the val Holryn's background. Are they descended from the valinor who served the Other? Belisarda? Some other Dude? Each explanation gets weirder than the last. So far as we know even the "Bastard Children of the Gods don't know.

My best guess at the moment is that they came into being as a result of the Bloodwar.