A man on Reddit is ditching his dad's third wedding to attend his sister's 21st birthday party.

In his post on the forum, the man explained he and his sister have the same father, but growing up it was clear he was the "golden child" as their dad "never wanted a daughter," resulting in her getting "overlooked." Their father-daughter relationship has always been rocky and "nothing she ever does is good enough for him."

The man revealed his sister is often "excluded from family gatherings," which "hurts her a lot," so he always tries to include and make himself available for her. Case in point: He promised his sister that he would fly out for her 21st birthday this July to buy her first drink.

"We have been planning this for months, and I already got the tickets," he shared.

There's just one problem: The man's dad is set to marry his third wife on his daughter's birthday. To make matters worse, his sister was not invited to their dad's wedding.

READ MORE: Reddit Backs Bride Who Refused to Replace Step-Daughter With Niece

"I told my dad I already had plans to fly down and celebrate Mary's birthday with her, and I wouldn't be able to make both events," he explained, adding that his father "seemed shocked."

"I'll admit, this pissed me off because the least he could do was acknowledge his daughter's birthday. I told my dad that I plan to spend my day with Mary, and the only way I will come to his wedding is if she is invited and decides to go," the man added.

His father was furious and argued that "birthdays come every year and weddings don't," despite this being his third wedding.

Even though the man's dad hasn't spoken to him since, and other family members have criticized him for being "selfish" and "ruining" the wedding, he's sticking by his decision.

"I'll admit that what I said may be harsh, but I also stand by it. I am not the one being selfish here, and if my dad wants his child at his wedding so badly, he can have all or nothing," he concluded.

In the comments section, Reddit users supported the man's decision to celebrate with his sister and slammed the dad for deliberately complicating things.

"What goes around comes around, and her 21st is a huge milestone ... it says way more about your dad that his wedding was scheduled to conflict with it," one user wrote.

"June 8 is such a deliberate move. I checked the calendar. IT'S ON A THURSDAY. Aren't weddings usually on a weekend so that they make sure people can make it and don't have to take time off work if they're coming from out of town?" another commented.

"He knows exactly what he's doing," someone else shared.

Celebrity Family Feuds

More From 106.9 KROC-FM