A MUM has been left stunned after a DNA test revealed her dad was not her real father and that she has three half-siblings.

Jaclyn Baxter, 33, spent her life thinking she was an only child until she did a genetic test, reports The Sun.

The California mum-of-two discovered her father Gary Ralph, who died when she was 18, was not her real father while researching her family’s medical history.

She decided to use a saliva-based DNA kit from 23andMe, which gives customers a profile of more than 80 genetic traits, to find out about her children’s future health risks.

She was worried about passing on genes for Alzheimer’s or Type I Diabetes — illnesses that ran in her family — to her two young children.

Mrs Baxter decided to select the option where the testing gives you information about genetic relatives, even though the company warns: “In rare cases, participation in DNA Relatives may reveal that you are related to someone unexpected, or that you are not related to someone in the way that you expected.”

When the test came back she discovered her genes were healthy, she had British, Irish, French and German heritage, and a half-brother named Loren Chase.

She tracked him down on Facebook and when she saw his picture she said: “Holy s**t, that’s my smile.”

She sent him a message and he quickly responded: “Jaclyn, Wow! Yes, I am definitely open to connecting. I have so many questions!”

Mr Chase told her she had another half sibling called Tim McNulty of Irvine, California.

The three sent a flurry of e-mails and began to get to know each other.

In her blog Mrs Baxter, who is estranged from her mother, wrote: “We were understanding of each other, and the security and comfort was already here because we had so much in common and got along so well.”

Mrs Baxter discovered both of her brothers’ mothers fell pregnant using donor sperm, apparently from her father.

A DNA lab confirmed that they were all siblings but a cousin, Kelly, had a daughter who had taken the 23andMe test but was not in Ms Baxter’s top 2000 genetic matches.

Confused, Mrs Baxter asked her dad’s sister to test her DNA and discovered they weren’t even distantly related. She had been conceived using a sperm donor.

But she said: “My dad is still my dad, and now I have three siblings, and family. It was lonely being an only child, with both my parents being gone out of my life, and my brothers and I share a bond in common that most can’t relate to. The more I get to know them, the more excited I am to belong to this unconventional family.”

But she does admit to sadness about her father, and said: “When I found out that my dad isn’t biologically mine, I felt robbed of that beautiful moment. I try to tell myself that I can still think fondly of my dad when I see his cute dimpled chin, but somehow it’s just not the same.”

Mrs Baxter met Mr Chase for the first time in June, then Mr McNulty in July, before all three met shortly after.

The trio decided to submit their DNA to Ancestry.com and found another sibling, a 35-year-old half-sister named Andrea Hugel Knosp, from Fort Polk in Louisiana. The pair have now been in touch and are getting to know each other.

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This story originally appeared in The Sun and has been republished here with permission.