Living next to a sex offender... he's my uncle *update*

My husband and I moved into his childhood home when his parents bought a new house. This one was a gift and payed off. We have been here 5 years. Well about 3 years ago my Aunt and her husband moved in next door. My aunt's husband is a sex offender and has been almost their whole marriage of 30 something years. She forgave him so our whole family kind of remains amicable but distant with him. Growing up, us kids were told to stay away from him. Well since moving next door, I have seen him with a young trashy blonde girl that I am assuming is a prostitute. He is in his 60's, super fat, and doesn't have any money of his own... It disgusts me. They go inside and rush back out usually less than a half hour later. I took pics from a distance the first time and sent them to my mom who had one of their sisters show her and do a heart to heart talk. She still stayed with him. She told the family she was living on the other side of the house and she didn't want to leave him because she didn't want to be alone. Well supposedly it had stopped... I started working more hours and have not been home during the day. Now, I am on maternity leave, and my first day home I see that same girl go inside with him. It makes me so mad and I don't know what to do. My Aunt supports him and works a full-time job making barely more than minimum wage. How do you help someone that wants to pretend like nothing is happening?

**update**

I told my mom everything I saw so she decided to have a heart to heart with my aunt in the driveway. Turns out my aunt knows, but she is 60 something years old and doesn't want to change. They don't have sex and they don't share a bedroom. Well after my aunt went back to her house I was outside talking to my mom, and he comes running out of his house yelling. He was telling my mom in very unkind words to mind her own business and to leave his family alone. I'm pregnant so I went straight inside. I don't think he ever stepped foot on our property (I don't think he is legally allowed to because I have a toddler?). Still this has seemed to escalate and all I want to do is cry. We can't leave our home because everything is already paid for and it is the home that my husband grew up in. I'm just afraid of retaliation... what are my legal rights against sex offenders? We live in Florida by the way, so I know the stand your ground rule.