Marriage registered by fil is that not fraud?

Donot mind, be brave, it may not be wonder “only in India” once FIL shows up at Registrars Office as “true groom” that also of her “own daughter” and strange freakonomics incidence the Registrar also may not have objected to such queers in front of him and thus the alleged incidence might have happened and same transmitted to you as “good news”.

Above proposed inference of your mystery (may be also read as misery) besides the point here, actually what we see here is that your wife is restless and is on short supply of confidence level if and only if you would come back to her from overseas or she has to see again Runaway Bride Blue Ray Disk 7 more times! OR your FIL thought he can fix re-marriage of his already married daughter with someone else who stays as ghar jamai than you and has plans to file S. 498a – S. 406 IPC / DV Complaint / S. 125 CrPC hence he wants you to come back mid-way assignment and thus might have given you a mild smiley shock of such announcements.

Above are some of the possible reasons otherwise no law abiding citizen of India does such acts of omissions /commissions as what your FIL alleged to have been done as you say to us.

Yes your guess of ref. property is as good as mine and if happens quite easily too just by showing Xerox copy of property docs.

So keep your guards up 24X7 and ask him (FIL) politely tonight to scan alleged Marriage Registration Certificate to you saying I have to give to State (Home) Department for arranging her Visa and arrange for other formalities and then you discover what you have to then discover and report enlargements here of such discoveries if you say you never attended Marriage Registration process before leaving for overseas, for next set of solutions and pondering over on your next query if any. 

Don't think that FIL has always ill will.  You said that you went to register your marriage and it implies that you may have signed the form.  As it is Hindu ceremonial marriage, there is enough proof that the marriage is real and not fradulent.  Invitaion card, photoes, signatures of witnesses on the form are sufficient proofs.  In that case marriage can be registerd by the registrar.  (At least in Maharashtra, this procedure takes place.  I am unaware of the process in Delhi.)  Still, remaining cautious is always good.