Well, I must say struggled to understand quite a lot of that, as the grammar was terrible, (sorry, but if the grammar is bad, it is hard to understand something. Try reading your posts back to yourself after you have writen them to make sure they make sense) but I shall try to answer the question as best I can
It is quite possible that Legolas and Arwen are related, but without some extensive research, I could not tell you how, or who is the person who makes them related. [If they are related, it is most likely an elf in the kingdom of Doriath in the first age of middle-earth who is the link]
but something else you have to remember is that Aragorn and Arwen are related, albeit very distantly.