I imagined him being 36-37 at the start of Inquisition, to keep him roughly in the same age range as my Aeducan. I made a post about his childhood (which wasn’t pretty) on the BSN so I’ll copy and paste it here.
Faith is a luxury to those whose lives have always held comfort and tranquility, and a refuge to those whose desperation for something greater inevitably has them gravitate towards it, especially in the face of adversity in their own lives. I have never really had faith, not in higher powers nor in people. How could I? Born as I was, living as I am… – Nasir Cadash, as he conversed with Cassandra in Haven.
While most Dwarves in the Carta are born outside of it and end up joining, Nasir was one of the few – lucky or unlucky he has never determined – to be born squarely in the Carta. The youngest child of the Cadash Syndicate’s leaders (born 9:04-9:05 Dragon), he was never expected to take control of the entire operation but be merely another one of its leaders. He had every opportunity to learn however, as his parents felt that a child such as he should not become merely a brute who couldn’t think of himself – even though his father, being the Dasher, is himself a very violent brute.
When he was thirteen, they had sent him on his first official mission for the Carta. A Dwarf named Oskias (different one then DC origin Oskias) had pilfered some lyrium that belonged rightfully to the Cadash family, and Nasir’s job was to get it right back by any means necessary. He hadn’t really known what to do, so he just did what came to his mind first. He ran up to Oskias and played the part of a lost little boy, who had gone without food for several days. Oskias took pity on Nasir and gave him some of his food while taking him to his home in Kirkwall. From there, it was easy for Nasir to find the small container of lyrium.
When Oskias came back with some tea, Nasir used a bit of deathroot he’d found in the wilder regions of Sundermount and taken the extract from to give Oskias some slight poisoning. He ended up leaving the room saying he needed to rest and that Nasir was free to stay the night, and as he stumbled away he muttered about “pink griffins”.
Nasir then grabbed the lyrium and ran as soon as Oskias passed out, returning to the established meeting place. He was congratulated for his work and brought back to his father, who sat like a king in the Cadash Syndicate’s palace out in Starkhaven (they have operations everywhere in Ferelden, Orlais, and the Free Marches). Unfortunately, he ended up learning about a month later that Oskias was found hanging in a tree, his limbs pulled as far as they could go and he was rent asunder.
That told Nasir the true nature of the Carta, something he hadn’t realized at all. All he knew was that his life was one of affluence that he attributed to mere mercantile efforts in various fields (banking, goods, mercenary companies) but he didn’t realize the true and brutal aspects that led to this life.
He became disillusioned with it at that point, but didn’t have the courage to run away. Part of that I suppose was him believing that he could ascend the ranks and take control so as to turn the Carta legitimate and respectable. A boyhood dream, and one he believes he’s grown out of. So he continued working for the Carta, doing odd jobs, eventually picking up a sword and shield and guarding caravans or going to certain areas to buy and sell smuggled goods. He quickly climbed the ranks because he was so adept at any task he was given and eventually earned the right to be a commander of a mercenary company that operated in Ferelden, as a means to see if he could be their liaison and overseer of Fereldan operations.
It wasn’t until the Fifth Blight, when he was twenty-five years old, that he met Xanthos Aeducan. The two of them met on the wayside up near Highever as Xanthos was on his way to Orzammar, and established a camp in the same vicinity. Though Nasir knew he could earn a great deal of coin for the Cadash family by turning over the leader of a group of an outlawed order, something within his being told him that he shouldn’t. And he couldn’t quite place it.
Eventually, as he talked with Xanthos, he felt something deep within his spirit. He felt…. like there was more to be gained from working with this young Dwarf then there was in the Carta. He felt a connection to this man, not romantic in nature but more…. akin to being a proud Dwarf, one who could hold his head up high.
As it happened, his business was taking him to Orzammar as well for business, and Xanthos convinced him to be his eyes and ears within the Carta. It was a private meeting between them, you see, but it was here that he met Leliana, Morrigan, Darius Brosca, and Shale (among a few other people). He wouldn’t learn that Shale was his ancestor until after Xanthos returned from the Deep Roads, but it was still an interesting encounter for him.
As for his faith, he’s always believed in the Stone, and he’s always felt a connection to it. But he’s always felt that he wasn’t worthy of that connection because he was a part of the Carta. He considers it his great shame, and much as he feels he’s now a better person for having met Xanthos (whom he considers a friend) and actually standing for something beyond money and prestige, he doesn’t quite feel he’s worthy of being returned to the Stone.
So his faith, while there, has never been strong. And thus he says the line above. Though you might be asking yourself now “Doesn’t that line contradict what you’re saying now?”. On the surface, yes it does, but as he is Xanthos’ eyes and ears and he’s loyal to the King of Orzammar he can’t let it slip that he’s doing things for the good of Orzammar or that he holds an allegiance to them, especially when he’s one misstep away from falling into the fire about being responsible for the Conclave’s destruction (as Orzammar and the Carta would greatly benefit from the Mage-Templar War).
Leliana and Morrigan are also working to advance Orzammar’s interests, but Leliana – being a bard and all – knows how to keep her loyalties fluid enough. So she’s loyal to Orzammar and the Inquisition, figuring that she can do what’s best for both (a route Nasir doesn’t know how to adequately do and often struggles with). She recognizes Nasir when they meet in prison, but she doesn’t actually know that Nasir is also working for Xanthos. She wasn’t around for that discussion the three Dwarves had (Darius Brosca being the third).
And if you were to ask him what he missed about Carta life, he would say the friends he made there. He was respected and loved in his mercenary company – basically like Thom Rainier, but without the Callier Massacre – and he had people who would give him his all. And he made sure to give them his, until he lost most of them in the Conclave (made his PTSD worse, and Inquisition basically makes him feel worse at multiple turns. Haven, Adamant, etc.)
I should also mention that he has three siblings: Viktor Cadash (the eldest), Vaida Cadash (second eldest, has a few posts), and Soren Cadash. Their relationship is pretty strained, between all of them.
I haven’t given much thought to Viktor other then that he was perhaps Trian taken up to 11, but Soren was a reclusive, bookish type who was good with words. Vaida was the hitwoman of the Carta.
Here’s a picture of her:

And a blurb about her relation to Nasir:
Vaida is his elder sister and she was raised to be the Carta’s hitwoman. She doesn’t give much thought to a life outside the Carta, and when she pops up to visit Nasir at Skyhold she tries to goad him into using the resources to help the Carta become stronger (just the Carta). He refuses to do that, saying he’s through with a life filled with nothing but greed and blood without purpose, and they argue.
And while she’s ruthless, she does care for Nasir, because she feels she took him for granted growing up. So she’s glad he’s alive. In the end she and Blackwall hook up together.
Though considering I make a LOT of poly ships, she’d probably be poly with somebody.