My question is that what is ilm e Jafar /jafra? And is this ilm so easy to attain that every individual can claim that he has this ilm? Where I live people, who claim that they have this ilm, they are usually busy in telling people about there future like with whom they will get married or when they are going to have a child etc? So by attaining this ilm all a person does this and could it be called right?

I have read that Huzoor s.a w has this ilm and he passed this ilm to Hazrat Ali a.s and through him, all the Ale Mohammed are the successor of this ilm. If it is right, then not surprising because all the imams possess the knowledge of unseen. What I wanted to ask is that some claim that this knowledge has been a miraas of Syeds and where I live some Syeds claim that they possess this knowledge. And how is this ilm different from fortune telling or astrology etc which is forbidden in Islam?

Ilm ul jafr is a science related to Ahl Ulbayt.
It is not with any body other than Imam u Zaman AS, as narrated by Imams AS.
What those people are telling is not true.