Aribeth del Tylmarande claimed (in Neverwinter Nights 1), that her family was killed, and that she was the sole survivor. She canonically dies in the events of the game (her fate is ambiguous, but NWN2 explicitly states she is dead). This implies that Seldra is a more distant relative (although there's probably more information in the adventure I'm not privy to). I highly doubt that, given her duties in NWN1, that a fighting Paladin of Tyr would allow herself to become pregnant, so it seems unlikely that Seldra is a direct descendant.
What has me curious is how Seldra can hope to claim to be an heir of Nasher, crown or no crown. A secret liason between Aribeth and Nasher doesn't seem probable...
Not to mention, her lineage would be suspect anyways, as Aribeth was likely killed for turning traitor, after her corruption by the Sarrush.
but do whatever you want
Speaking as the author of the adventure, it is indeed an Easter Egg for players and DMs familiar with the game. (Also, fun fact, the badges the Lost Heir hands out at the end of encounter 2 are supposed to look like the purple "weeping eye" symbol of Neverwinter.)
In the course of "Lost Crown," Seldra claims to be a niece of Aribeth, not a direct descendent. There's little evidence to support this claim one way or another, and it's left as a plot thread for DMs to use however they like.
Seldra does NOT claim to be a descendent of the Alagondar line--in fact, she specifically states that she is NOT a scion of Alagondar. Read the adventure. It'll answer your questions on this point. 
Also, I'm pretty sure "Lost Crown" isn't considered canonical, so you should feel free to do whatever you want with it without feeling like you're straying from canon.
Cheers
(Also, fun fact, the badges the Lost Heir hands out at the end of encounter 2 are supposed to look like the purple "weeping eye" symbol of Neverwinter.)
Eric, what about the badge that Neverember gives them? Did you have any particular image in mind for those?
it's an Eyye with three tears on it
ever see the neverwinter nights game boxes.
it's an Eyye with three tears on it
Is that in response to me?
Lord Dagult Neverember has his own sigil, which I don't think made the cut into the Neverwinter Campaign Setting. Unless you find a better answer elsewhere (you might ask Ed at Candlekeep), assume that it's similar to the Waterdeep sigil, though no doubt Neverember has added his own personal device. Possibly an eye like the Neverwinter symbol, to (not so) subtly imply that he is a rightful heir. Seems like something he would do!
Cheers
the savage north or some other 2nd ere book actually describes it and stated that it was on the badge of the greycloaks.
how the crying eye came in to be IIRC I do not know.
unless it has something to do with the fact that Tyr appeared in the city of skilled hands during the time of troubles.
and yes I was describing the neverwinter eye...
so if I misread something I do appologize
Gimper, I think SFD is describing the Heir's symbol, which is the old school Neverwinter symbol.
Which is exactly what I thought, and why I wondered if he was replying to me, or to someone else.
Lord Dagult Neverember has his own sigil, which I don't think made the cut into the Neverwinter Campaign Setting. Unless you find a better answer elsewhere (you might ask Ed at Candlekeep), assume that it's similar to the Waterdeep sigil, though no doubt Neverember has added his own personal device. Possibly an eye like the Neverwinter symbol, to (not so) subtly imply that he is a rightful heir. Seems like something he would do!
Cheers
Correct. There's no sigil shown in the NWCG. I saw online an image of the weaping eye that was gold, not purple. I thought I might incorporate that.
Ideally, I'll try to incorporate this
Into this (maybe for the reflected image in the water)
Thanks Eric.
the eye thing was IIRC was not even neverwinter's original seal.
the savage north or some other 2nd ere book actually describes it and stated that it was on the badge of the greycloaks.
how the crying eye came in to be IIRC I do not know.
unless it has something to do with the fact that Tyr appeared in the city of skilled hands during the time of troubles.
and yes I was describing the neverwinter eye...
so if I misread something I do appologize
No problem. It just confused me because I was asking about the badge that Neverember gives to the players in the Encounters adventure that Eric was talking about. I don't know if you played that adventure, but the Lost Heir gives the PCs a badge (which Eric said is the purple eye) and Lord Neverember also gives the PCs a badge.
"The royal badge of the city is a white swirl - a sideways "M," with points to the right. It connects three white snowflakes; each flake is different, but all are encircled by silver and blue haloes." - Volo's Guide to the North (pg 131)
As to where the eye came from, first place I ever saw it mentioned or depicted was in the original Neverwinter Nights game, and it just sorta stuck around for whatever reason.
or when the info was passed on to bioware, they got dark sun stuff instead..... but then I dont have any of the dark sun stuff
Cheers