A lady told me in conversation, that she knows a young lady who was born in March 1991 (that would make her 21 at present time) and she has a four year old daughter. If the guy in question who is more than twice the young lady's age, is the children's biological, will that fall under statutory rape?

Depends on where if the child is 4 that means she conceived when she was 16 or 17. In many states, age of consent is 16.

There probably is a statute of limitations on statutory rape that probably expired.

Your language is confusing me. Children or child?

SO - someone had a child 4 years ago. She's 21. Four years ago she was 17. We'll call her X and we'll call the child Y.

X and Y are BOTH the biological children of the father of X?

Where?

My other concern is that you posted a complicated issue once before. When asked where, you never responded, despite people spending time and effort to help you. https://www.askmehelpdesk.com/real-estate-law/how-get-problem-tenant-out-who-knows-how-work-system-670706.html