(CBS) – It was a bittersweet Christmas morning at LaRabida Children’s Hospital, as the man who has portrayed Santa Claus for more than 40 years handed the torch to his son.

Paul Mesirow first volunteered to portray St. Nick in 1971. It went well enough with the children that the hospital asked him if he’d do it the following year.

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“I said, ‘I’ll make you a deal. As long as there are kids in the hospital on Christmas, I’ll be back,’” he tells CBS 2’s Sandra Torres.

Along the way, his son Michael, now 31, was born.

“I’ve been coming here since I’ve been six months old, watching my father portray Santa Claus,” the junior Mesirow says.

This year, it was his job to get into the Santa suit. His father has ALS and was no longer able to provide the service.

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“My ‘ho, ho, ho’ got up and went, went, went,” Paul Mesirow cracked Friday.

He says he’s sad to give up the reindeer reins, but glad that his son is taking over.

“He did wonderful today. It was a pleasure watching him. I have nothing but good words to say about his Santa Claus,” Paul Mesirow said.

Chicago Fire Department Engine Co. 63, as always, accompanied Santa to help deliver presents to the young patients.

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