If I suspect something like this then I will take following measures:
1. Confirm my suspection through observation.
2. I will gather evidence like witnesses, records, documents to build a strong legal case.
3. Communicate with testator, who is being manipulated to know the true intentions.
4. Will proceed to legal remedies and challenge the improper will or trust by filing a complaint in probate, guardianship, etc.
5. Also, I will report under elder abuse to protect these vulnerable child.