שלום וברכה
1. I see a confusion here, the Yona Ashkenazi was the בעל איסור והיתר, he had a grandson who was also named Yona Ashkenzi
2. According to the information provided by the grandson Yona Ashkenazi, was the איסור והיתר were a son-in-law of the Maharam of Lublin.
3. What is being said here that his father was a מחותן with the מהר"י ווייל is not necessarily talking about this child.
In total, the איסור והיתר was probably a son-in-law of the Maharam of Lublin.
Please comment if I am correct
הצלחה ברכה