If you know or suspect children are being abused, then you need to report it to ensure their safety.
However, like
@Annalyn78 said: do you know? (have they told you? Have you seen signs? Do you recognise patterns of behaviour?)
Or:
do you think because she abused you when she was a young child that she is going to abuse (her) children as an adult? Because one doesn't mean the other. And be careful with this. You got to ask yourself some challenging questions here. Are you in therapy as that might be a good place to explore it?
I reported my sister, her husband, and their children to child protection services (not police). Not because of sexual abuse. But of drug use, alcohol problems, and neglect. Which I knew was happening as I saw it, and my sister's friends were telling me what was happening. The child protection services did nothing at all the first time I phoned. The second time, they investigated by talking to my sister and her husband and the kids and the school - no drugs tests, no unannounced visits, no real exploration. And they just accepted their account and dismissed mine , and did nothing again. And then finally, they intervened when the police got involved removed my brother in law from the house, and child protection made sure my sister knew if he returned: kids will be removed from her. My sister now knows it was me who phoned them, as do the children. It's not always been easy (some of the children are angry with me that I phoned, as is my sister, and others are happy I did and were wondering and angry about why no one stepped in earlier).
Only you know what you should do as only you know your situation.
It's not easy either way.
But: children need to be safe. I do not at all regret what I did, because their safety is far more important than my relationship with my family (all of which has been impacted as everyone, my parents , my sister, blamed me). However, I knew for certain that this was happening.
So, you need to ask yourself what it is you know versus what it is you are worried about and potentially projecting? Difficult thing to work out.