This discussion clarifies whether a widow and her son can establish a Hindu Undivided Family (HUF) and if the mother can be appointed as the Karta. While a minor son cannot be the Karta, his mother can act as the Manager. The consensus is that there's no legal impediment to a mother and son forming an HUF together.
17 September 2024
If the son is a minor then his mother will act as Manager of HUF. In my opinion, there is no bar in forming an HUF by mother and son.