Is it Wrong or Right

So I know this couple who I just recently found out was half brother and half sister they apparently share the same father. Course when I asked how it happened how they became boyfriend and girlfriend...all they could say was they did not grow up as siblings together...they did not have the bond of a brother and sister. He is 16 years older than her. They have their relationship ups and downs just like anybody else does and they seem to be very much in love and they have been together for almost 3 years...even talking about possibly having a baby together. Anyways what I would like to know is other peoples opinions...I think love is love and you can not help who you fall in love with. Also I think about LGBT...would it be much more difficult for this couple to be excepted than it already is for LGBT couples?