Yes he is her son if the following is correct but there are no sources to confirm. This website can be questionable so use at your own risk.
11 Jun 1570
There is a full discussion on whether Jehan is the son of Anne Somerset and her husband Thomas Percy , Earl of Northumberland on Jehan's profile. https://www.wikitree.com/wiki/Percy-562
The couple are not linked as parents since there is no proof of any relatioship
According to the profile editors, Thomas Percy died without a male heir and his titles were inherited by his brother Henry.