Property related query on the property given on rent to relative for 15 years

2 years ago

In brief I owned jointly a house at Allahabad with my two brothers who are not alive which my father left us who in turn shared the house with my uncle. Since we are not staying in that house nor my brothers or their family because of our working place was in different city. My father and uncle had been living and made separation of their choices. After the demise of my father, our portion was given to one of our distant relative who used the same as her clinic and still using it as clinic with her husband who is also a doctor. A nominal amount as rent is given by her as rent with no receipt no rent agreement since then say 15 yrs or so. The amount was collected on our behalf by my uncle's son. Also my mother was living in my uncle's portion till 2015 when she expired. There some understanding between the doctor ( relative)
and my Uncle's son occurred as my uncle's son want to illegally occupy our portion too with the connivance of doctor( relative now in position of our portion). We want to get back our premises back. how should we proceed ....Shall we force in our house with my family in our portion which I think doctor can do nothing about. One important point I missed id that title deed is not with us which is in the name of my father and uncle, its probably with my uncle's son. Kindly guide me how to proceed to get back our portion. Another fact is that there is an entry point of uncle's potion to our portion and the rest has separate entries.
If you want to know other details kindly say so or give me advice. Thanks