Karma Brown and her boyfriend had only been dating for three weeks when they were forced to decide whether they wanted to have children together.

Brown had been diagnosed with cancer and her treatment would leave her infertile.

The new couple decided to take the plunge and have her eggs fertilized and frozen. Three years later, when Brown's post-recovery efforts to become pregnant had proven unsuccessful and they were running out of chances, Karma took her sister up on an offer to help.

Now, Jenna Davis, a 34-year-old acupuncturist and chiropractor from Burlington, Ont., is six-months pregnant with her sister's child and both are looking forward to the new addition to the family.

  • Read the Browns' baby blog

Davis told Canada AM she didn't think twice about offering to serve as a surrogate mother.

"It wasn't a question," Davis said. "We always hoped that would be the last-case scenario and that she would be able to experience that. I had just had my daughter, I had a four-month-old at that time and couldn't imagine her not being able to have a baby."

Brown, 35, from Toronto, said it wasn't difficult for her and then-boyfriend, now husband, Adam to decide they wanted to have children together.

"There were so many difficult decisions we were trying to make at that time and we knew we wanted to be together so we did the leap of faith," she said. "(We said) 'If we want to be together this is what we have to do now to make sure we have that opportunity in the future.'"

Three years later, when her cancer was in remission, the couple began trying to become pregnant through in vetro fertilization.

"I truly believed, I was led to believe, they'd just put the embryos in and I'd get pregnant with twins," she said. "My biggest problem would be to decide what to do with the other 18 embryos that we had. It just didn't turn out that way."

That was when Davis stepped up to help, making the pregnancy a full family effort.

She told Canada AM her husband and children all support the initiative and are excited about the role they are playing in the process.

"My kids -- Emily is five and Gavin is three -- to them this is completely normal. We just said Auntie Karma's tummy is broken so mummy's tummy is going to carry their baby."