i heard abhir last line he is going to barbaad his friends family meaning bhawri [my opionion ]
and bhoomi and abhir cant be siblings i am sure of that otherwise ekta maai dont show too much of their nok jhok coz they gonna be together in future thats my 101% instinct.
This has definately to do with karan and i think mandira must've adopted this kid from somewhere i dunno or he might be meera's relative coz this r the only two ppl who is not fond of Karan.