When Larkin was diagnosed with pulmonary hypertension, the news devastated her because it meant she couldn't become pregnant. Larkin's mother, Kozisek, then took it upon herself to ensure her daughter would get the family she wanted.

Pulmonary hypertension is the result of high blood pressure in the lungs and heart that can cause heart failure if left untreated. Women with pulmonary hypertension who become pregnant endanger not only their child’s life, but also their own.

"I've always been close with my mom even before this so that hasn't changed and I'm grateful she will have such a special bond with her grandkids," Larkin told ABC News.

This isn't the first time that Kozisek has agreed to the generous and selfless act of being a gestational carrier. She also carried and delivered Larkin’s two-year-old daughter Harper. No health complications were reported from either pregnancy.

gestational carrier is a woman willing to carry the pregnancy of another woman who is unable to give birth. The biological mother and father undergo in vitro fertilization to extract egg or sperm, which is implanted in the willing carrier’s uterus.

"I heard about the procedure on a talk show and decided to check out the possibility of me doing this for them so they could have kids of their own if they wanted,” Kozisek told ABC News.

Even Dr. Jani Jensen, who performed the in vitro fertilization process for Ashley and Susie, said that this was an unusual situation, although a family member acting as gestational carrier is fairly common.

"It's usual for a mother to act as a gestational carrier for her own child and she was at the older end of the spectrum for pregnancy," Jensen told ABC News.

"But she was a good candidate because she'd carried previous pregnancies successfully and was in excellent health."