Only one lineage?

[Tar Elenion]

According to Manwe *everybody* with *any* mortal blood is automatically accounted mortal (unless I've gotten that quote wrong too). According to this rule Arwen and the twins would have been *mortal* dispite their Elven mother.

Unless Manwe granted them other Doom. It was within Manwe's prerogative to grant 'other doom' as he saw fit.

I argue that Elrond's offspring were given the option of choosing Immortality because the grace granted to Earendil and Elwing was extended to their grandchildren as well as their sons. If this is so than logically the same grace would have been extended to Elros' brood.

That is not what JRRT says. JRRT says:
"Elrond chose to be among the Elves. His children - with a renewed Elvish strain, since their mother was Celebrían dtr. of Galadriel - have to make their choices."

Legolas' suggestion that Elrond's children were offered that grace out of compassion for their parents, (so they might not lose their children) is possible but not particularly likely as such graces are not granted out of sentiment but as a reward for great deeds affecting the destiny of Arda.

JRRT states that, with their renewed Elvish strain, Elrond's children have a choice. He says Elros chose mortality and so his descendants are all mortal. Elrond had done no great deeds affecting the destiny of Arda when he was granted his choice. Thus there is a reason they were granted a choice. To allow them to decide whether or not to be forever seperated from their kindred is a more likely reason than Manwe extended the choice to the grandchildren of Earendil and Elwing(who were not even born), as well as their children. Especially since JRRT says Elros was mortal so his chidren were mortal.

[ March 31, 2003: Message edited by: Tar Elenion ]