okay I have been watching this serial from day 1 and here is my theory on shyam's identity. I dont think he is anajali's husband. I am guessing he is their step brother. Maybe arnav's father had an afffair with shyam's mom and decided to leave the family for her (thats why arnav hates marraige) and then arnav's mom committed suicide as nobody was ready to marry his sister and they got pushed out of the house. Maybe thats why shyam does not want to see arnav as arnav will kill him. Later on when they will develop the love triangle and when khushi-aarnav get married, maybe shyam will come with his father and stay at their place just to trouble khushi ( we know he is going to turn negative)