It is traditionally the children who give their dads the presents on Father's Day.
But when 24-year-old Brian Zollman was hospitalized with kidney problems and desperately needed a donor his dad Steven swiftly did away with all of that - offering up an organ to save his son's life.
After going under the knife on Friday, the pair, from Longwood, Florida, spent the Father's Day weekend recovering in hospital in ward beds side by side.
Brian, who is a recent graduate of the University of Central Florida, has suffered from kidney problems throughout his life.
He was born with a defect in the valves between the kidney and bladder but after many operations when he was a child, the condition was deteriorating.
When doctors said last year that it had got to the point at which he required a transplant, his parents both quickly offered themselves up as donors.
Steven, 54, was found to be a suitable donor and the procedure was arranged for this weekend at Florida Hospital Orlando.
Before the operation, Steven said: 'I'm giving my son a kidney and as you can expect we are kind of nervous.
'It's not your everyday gift but I just want him to have as good a life as he possibly can.'
Son Brian added: 'My kidneys have been deteriorating very slowly over my entire life but they have been watched by doctors.
'I believe the plan was to test everyone in the family until we found someone.'
Speaking of his father's gift, he added: 'I have no idea how to say thank you. What kind of Father's Day gift can live up to this?'
Hospital spokeswoman Jennifer Roberts told the Orlando Sentinel that Steve would be out of the ward in a few days, having undergone a minimally invasive procedure.
The greater risks involved with receiving an organ transplant mean Brian Zollman faces a longer recovery and is almost certain to remain in hospital for at least a week, where he will be treated with anti-rejection drugs.
More than 111,000 are on the waiting list for organ transplants, according to the United Network for Organ Sharing.
KIDNEY DONATION: WHY IT IS SO HARD TO FIND COMPATIBILITY
There are many hurdles to navigate when a patient requires a kidney transplant.
In almost all cases the donor and recipient have to have compatible blood group. With more than 100,000 patients on the organ transplant waiting list in the U.S., family members may put themselves forward to donate a kidney - but not all share blood groups so often the match is not so easy to find at home.
Most donated kidneys, in fact, come from deceased donors rather than family members. Since medication which prevents rejection is now so effective, it is not essential that donors are genetically similar to recipients.
Blood group incompatibility between donor and recipient used to be considered an absolute biological veto against proceeding to transplantation because antibodies present in the recipient's blood can cause immediate and catastrophic rejection of the transplanted organ.
A new procedure, however, has changed all that. It involves giving an extra anti-rejection drug (Rituximab) to help switch off the cells that generate anti-blood group 'A' antibodies in the recipient's body. A further treatment called plasma exchange removes the antibodies that are already present in the patient's blood.
The plasma exchange treatment needs to be carried out several times before the transplant operation to ensure that the recipient's body accepts the new kidney.
After this, as with any kidney transplant, the recipient then has to take routine anti-rejection drugs indefinitely.
Further requirements for kidney transplants vary from state to state. Some programmes limit the age one can be to donate or to receive an organ and others insist the patient is otherwise is good health.
A patient may be excluded from the list for suffering from cardiovascular disease, incurable terminal infectious diseases and cancer.
People with drug problems and or mental illness may also be excluded.
“You Have the Power to Save Lives – Register to be an organ and tissue donor & Tell Your Loved Ones of Your Decision”
United States, organdonor.gov (Select your state - top right)
Great Britain, register at NHS Organ Donor Register
Australia, register at Australian Organ Donor Register
Your generosity can save or enhance the lives of up to fifty people with heart, kidneys, liver, lungs, pancreas and small intestine transplants (see allotransplantation). One tissue donor can help by donating skin, corneas, bone, tendon, ligaments and heart valves
Has your life been saved by an organ transplant? "Pay it forward" and help spread the word about the need for organ donation - In the U.S. another person is added to the national transplant waiting list every 11 minutes and 18 people die each day waiting for an organ or tissue transplant. Organs can save lives, corneas renew vision, and tissue may help to restore someone's ability to walk, run or move freely without pain. Life Begins with You