"It was a wonderful day in ME when Barbara married her love and Craig joined our family", she wrote.
In another photo, Bush Hager held onto her sister in a loving embrace.
"My heart exploded last night as I watched my dearest sissy get married in Maine. It was just like her: private (only family!) and full of love (and yes lots of tears!)", she wrote.
The wedding ceremony was a true family affair, with the bride's aunt Dorothy Bush Koch officiating.
According to People, only 20 family members were in attendance at the low-key ceremony, held at the Bush family's compound in Kennebunkport, Maine. Barbara's parents, former President George W. Bush, 72, and former First Lady Laura Bush, 71, were there, as was her grandfather, former President George H.W. Bush, 94.
The couple will live in NY.
The addition to the family comes after a year of loss for the Bushes.
Former first daughter Barbara Bush has gotten married.
"It's just been a very sweet romance", Bush told People.
During the emotional toast, her grandfather was standing right beside her. Jenna also explained that her sister's "something borrowed" was a bracelet Bush Senior gave to her grandmother on their 70th wedding anniversary.
Bush Hager served as matron of honor, and her daughters, Margaret, 5, and Poppy, 3, were flower girls along with Coyne's niece, Emma, 5. Coyne is an actor and screenwriter whose credits include "Jarhead" and "Snowtown". "And we've been long-distance for most of it - he's been in L.A. and I've been in NY - but we've gotten to spend a lot of time together".