It can sometimes be difficult for our kids to have a healthful and happy relationship with both parents, particularly when one of them disappoints them or doesn't live up to their expectations. Your child might be feeling resentful toward his dad for several reasons, but by saying the right words you can calm the situation and help your child have a better relationship with his father.
Address the problem
Wait for a good opportunity to talk to your child alone about his feelings toward his father. You might like to have a little chat after a bedtime story or have a heart-to-heart talk walking home from the park. Say something along the lines of "Now, what is it about daddy that upsets you so much?" If you talk to your child when he is feeling calm and happy, you are more likely to find out where the resentfulness comes. Do not assume you know why your child is feeling resentful, just because you might be disappointed his dad didn't take him swimming last week. Your child might have a completely different reason.
Once you know the root of the problem, stay positive and be supportive toward the father. Do not agree with your child or say something such as "I know, Mummy is also angry with Daddy about that," even if it's true. If your child is resentful because his dad has to work late, you might say something such as "It is sad Daddy has to work so late tonight, but I know he really loves you, and he is looking forward to spending time with you over the weekend."
Talk with the Father
You need to talk about the issue with his dad. Depending on the relationship your child has with his father, it might be that he has no idea his child is feeling resentful toward him. Approach the subject sensitively because no parent likes to hear that his child is resentful toward him. You could say, "Have you noticed he's been acting a little different recently?" Suggest he takes some time to talk with his child alone about the issue, and then encourage some quality father-and-son bonding time. They might like to play soccer together in the park or take a trip to get ice cream.
Build on the Father-son Relationship
It isn't healthful for your child to have feelings of resentment toward his dad, and you will need to do your best to ensure they have a better relationship in the future. Your child will pick up on your own attitude toward his dad, so try to be positive. Depending on your circumstances, this might be tricky. If both parents are together, you can talk with your child about how great daddy is, and how excited you are to see daddy after nursery or school. However, if you are separated, you might need to talk about all the exciting things your child will do with their daddy when they see each other again. You might need to remind the father of any promises he's made to your child to ensure there's no further disappointment or resentful feelings.