Marriage!

[Encaitare]

And as for Aragorn, I think if Arwen was not Elrond's daughter[let's say Thranduil's] he wouldn't dare. Arwen was part mortal, right?

Indeed. Since she was the child of Elrond the Half-elven (actually I think someone here figured it out to be nine-sixteenths ) who got to choose between mortality and immortality, she too got that choice. I agree, though; if Arwen was entirely elven it is less likely that Aragorn would have pursued a relationship with her. Plus, the fact that he had Elrond's love and trust was doubtless helpful; he didn't have to go through that troublesome confrontation of the guy meeting his girlfriend's intimidating dad!