As per the I-T Act, if an assessee owns more than one house, then one house of his choice is considered as self-occupied & the remaining house(s) are considered as deemed to be let out.
However in your case you are already lettin-out your property on rent. so that would be considered your let-out property. The other house in which your parents are staying, that will be a self-occupied property.
in case of your leto-out property, you will be able to get deduction of Municipal taxes paid from your rent received during the year. On the balance you will get an standard ded of 30% for the expenses incurred. this deduction is of fixed amount, whether you incure any expenses or no. If there is loan going on on this property, then the interest paid on this would be deductioble from the rent paid.
in case of your self-occupied property, if there is any loan going on, then you will get the deduction of interest paid from your total income.
apart from teh above, you will also be eligible towards exemption from HRA, provided that you are paying rent.