[LadyBrooke]

The biggest difference I see between the two half-elven lines, is that Earendil, Elwing, Elrond (+kids) and Elros are related to the three kings of the elves (Elwe through Elwing, Finwe and Ingwe through Earendil, plus Arwen and her brothers are related to Olwe through their mother. By extension this means they're related to every royal Sindar, Teleri, Noldor, and Vanyar elf that exists.)

On the other hand the Princes of Dol Amroth are only related to a mere Silvan elf.

I'm not sure what the signifigance is but......