Joint Ownership Relinquishment & HRA

Hello I am from Mumbai. I live with my parents. We have two adjacent flats. 1. One flat is jointly owned by my Father-Mother & me. Ownership share/percentage is not mentioned in the deed. 2. Other flat is jointly owned by Father-Mother, me & my brother. Again ownership share/percentage is not mentioned in the deed. Since I own a house I cannot claim HRA and as such the tax outgo is substantial. Is it possible to relinquish my share or gift my share in both the flats to my parents or my spouse? Is it advisable to do so? Main question - Is there any illegality in the process? Since my main aim is to claim HRA. There is no loan involved & I had contributed financial while buying the flats. Thank You