The stress of having to work full time and take care of the children after his wife's death became too much for him, and he left his job to be a stay at home dad. He didn't know how to keep up with everything Jennifer had done to raise the family, such as cooking, enforcing house rules, and potty training.
Instead of planning and cooking three healthy meals a day for the boys, he operated like a fast food employee, reciting the various types of frozen food the boys could choose from ("Chicken nuggets? Corndogs? Mini quesadillas?"). His cooking skills were limited to making grilled cheese sandwiches and boxed macaroni and cheese, and microwaving frozen food. Jo addressed this with a shopping expedition to buy only fresh foods, and showed him how to make what appeared to be a paella.
He was in his late 30's when he appeared on Supernanny, it's unknown how old he is now.