She is your cousin
yes you can!
It is legal to marry first cousin in India. http://lawcommissionofindia.nic.in/reports/report212.pdf - Page 19
no....because she is a sister for you
You are their aunt or aunt by marriage.
Yes, he can. But he'd be marrying his step-aunt.
Such a person would be your second cousin, and in most places marriage between second cousins is legal.
A Hindu boy can marry his mother's sister's son's daughter if he can support her. This is legally acceptable on a Vivah Sanskar.
can it be an incest if a son and a daughter who are related because of their mothers who sisters marry each other?
Daughter hates mothers should she send mothers day card to daughter
it depends if its a step father or not. if it is a step father then ts completely legal. but if its his birth father then you cannot marry your cousin!!
Yes, although in that relationship there is likely to be a very large age difference, since that person is of the same generation as your grandparents.