John Bacon, USA TODAY

Logan Stevenson, the 2-year-old boy suffering from a rare genetic disease who served as best man at his parents wedding, has died, his mother said in a Facebook posting.

Christine Swidorsky married Logan's father, Sean Stevenson, Saturday in Jeannette, Pa.

"Today Logan was doing very bad. His breathing was very rapid then slowing down. I called hospice to come, and she checked him out and she said he's probably gonna pass," the Facebook post reads. "Sean and I held him all day he was comfortable with his medication then at 8:18 my son took his last breath in my arms."

"Logan passed away I'm so sad upset and I'm in disbelief. He is with angels and he's in no more pain. No more sickness no more hospitals. We love all of you for all your prayers thank you all for caring God bless you all! And most of all God bless Logan. I'll see you in my dreams my son."

Logan was born with Fanconi anemia, a disease that mainly affects the bone marrow and decreases production of blood cells. His parents moved up the date of their wedding so Logan could take part in the ceremony.

Logan stood with his grandmother, Debbie Stevenson, during a 12-minute ceremony Saturday uniting Logan's mother and his father.

"We're married," Swidorsky exclaimed joyously after kissing her groom to applause from family and friends.

After a whirlwind week, the Jeannette couple tied the knot in a hastily arranged backyard ceremony that formalized their union and celebrated Logan's life.

The Stevensons abandoned an original wedding date of July 2014 after learning from doctors late last month that their son had two to three weeks to live. The couple wanted Logan to see them marry and to be part of family photos.

Contributing: Associated Press