As we know that Ned Stark and Howland Reed are good friends. I haven't seen them on the picture pledging or fighting for house stark, Only about Meera and Jojen accompanying Bran Stark for a mission.
Jon didn't take the North in books. That's show only event. In the Books, Reeds did swear allegiance and fealty to Robb Stark when he was proclaimed King in the North:
Both Reeds were slight of build, slender as swords and scarcely taller than Bran himself. They went to one knee before the dais.
“My lords of Stark,” the girl said. “The years have passed in their hundreds and their thousands since my folk first swore their fealty to the King in the North. My lord father has sent us here to say the words again, for all our people.” She is looking at me, Bran realized. He had to make some answer. “My brother Robb is fighting in the south,” he said, “but you can say your words to me, if you like.”
“To Winterfell we pledge the faith of Greywater,” they said together. “Hearth and heart and harvest we yield up to you, my lord. Our swords and spears and arrows are yours to command. Grant mercy to our weak, help to our helpless, and justice to all, and we shall never fail you.”
“I swear it by earth and water,” said the boy in green.
“I swear it by bronze and iron,” his sister said.
“We swear it by ice and fire,” they finished together.
ACOK - Bran III
So yes they swore fealty to Robb (King in the North) and therefore to his heirs and successors as well.
No there is no mention of Reeds swearing fealty to Jon.
Meera returns to Winterfell only after Jon is gone to Dragonstone. Howland Reed himself never leaves his castle. Jojen is dead. So, there is no mention of Reeds swearing fealty explicitly to Jon.