Ryder Confirmed to be Brother/Sister

Good question. I hope we get to talk to the siblings

Well, probably you can assume she/he is 'somewhere'. I'd welcome the option for my sibling to be customizable at the beginning of the game, because I don't like default characters.
What I would like the best would be to have your sibling as a squadmate with a customizable face.

One thing is certain, incestous porn fanart will be off the charts.

Fergus Cousland, Kalah and Rica Brosca always survive Origins, regardless of the games events or if related to the Warden or not.

The Inquisitor's parents are never seen, but can surmise from how Trevelyan is often formally introduced as the son/daughter of Bann Trevelyan, that their father is presumably still alive at the time that Inquisition takes place.

In Mass Effect, if Shepard has the Spacer background, their mother Hannah Shepard is alive for all three games, escapes the Reaper invasion of Earth and spends most of ME3 leading the surviving Alliance fleets as a Rear-Admiral serving under Hackett.

Those are all the ones I can think of, so it does happen... even if it's rare.

(Edit: Ah, got pipped to the post)

I doubt your sibling will die in the beginning, the commentary to the video linked in the OP suggests he/she is a part of the universe - if not the story.

Was also wondering about this. I'm leaning more towards the former, where we can actually see and interact with the sibling for some amount of time. I'm just assuming since Mac has already emphasized the whole family aspect.

Hopefully they'll allow us to customize both genders as in Fallout 4. And hopefully they won't share The same fate.

Receive? 

A dynamic system would be interesting where their opinion can change on you 

I sure hope they'll allow freedom in defining the relationship with your sibling and father, it'd add a lot in roleplaying The PC differently.
Compared to DAI, the background is practically confirmed as a single one, so they might put the resources allocated in The different backgrounds on more options for the relationships with your family, or other background stuff.

Kinda cool that something people was suspecting since E3 is a thing. That the Ryder's are siblings.

When you go into the Carta hideout during the Orzammar questline, the (male) Dwarf Commoner's corpse is shown in the cell next to Leske, who refers to the events of that Origin and mentions that Brosca perished after they stopped eating one day. The events are also referred to in the Dwarf Noble Origin, where they refer to a castless duster who ruined a previous Proving by impersonating one of the warrior caste.

The guard at the gate of the Alienage refers to Vaughn being slain and Soris is later found in the dungeons of the Arl of Denerim's estate, confirming that some of the events of the City Elf origin happened, although leaving it unclear what happened to the City Elf.

Merrill confirms in DA2 that the events of the Dalish Origin happened. After finding the Eluvian in the forest, Tamlen disappeared and Mahariel eventually succumbed to the taint, leaving Merrill to attempt to rebuild the broken Eluvian, that seems to have been destroyed regardless of Duncan being present.

Jowan referring to his "trouble" with the Circle and showing up in the Arl of Redcliffe storyline shows that the Mage Origin happened, although it's unclear whether the mage that helped him destroy his phylactery was Surana or Amell. WOT2 also mentions Lily remained imprisoned in Aeonar for years, despite showing no signs she was a thrall to a blood mage.

The Cousland family were betrayed by Howe as in the Human Noble Origin, leaving Fergus as the sole survivor. This is confirmed in Awakening by both Oghren and in an epilogue involving Nathaniel saving Fergus' life, as well as via a war table mission in Inquisition.

The events of the Dwarf Noble Origin happened, with Bhelen having arranged Trian's murder and possibly framing his sibling for the deed. The default Aeducan was male and exiled to the Deep Roads, as mentioned by various people in Orzammar and confirmed in a letter from Endrin.