A transgender dad, who had given birth twice, says he found the strength and courage to transition after his step-daughter came out as a boy.

Spencer Hanson, 36, who was raised as a girl, said he always knew '100 percent' he wasn't really a girl.

Spencer gave birth to two children, Bug and Cub, while living as a woman with his wife Jess Hanson, 42 - who has two children to a previous relationship.

It wasn't until his step-daughter, Bub, announced when she was nine that she was a boy, and not a girl, that Spencer found the courage to begin his own transition.

He said the process of enrolling a step-child in therapy and starting them on hormone blockers gave him the strength to begin his own transition to male.

After having his second son, Cub, now five, in 2013, and suffering a miscarriage in 2015, Spencer began taking testosterone and had a hysterectomy and double mastectomy.

Speaking publicly about his journey for the first time, Spencer, who runs an Instagram blog called Becoming Dad, says he believes he would not be alive if it wasn't for Bub.

Meanwhile, Bub has begun another stage of their journey and is 'de-transitioning' back to a girl.

Spencer, of Kansas City, Kansas, said: "I always knew I was 100 percent not a girl, so when I got pregnant it was super hard and the whole thing gave me so much anxiety.

"Literally no one else on the face of the planet can be pregnant except girls and I did not know how to be pregnant and not be feminine.

"What kept me from transitioning is I felt like I was completely letting my parents down and I would lose them and my brother and my friends of many years.

"I don't like making people feel disappointed or ashamed in me.

"In 2010, I was at Walmart with my little Bub and I was like, 'Go and pick out some clothes.'

"My Bub was crying so I said, 'What is going on?' and she said, 'I can't be [birth name] any more. I will die.'

"I said, 'OK, who are you?' She said she was male and was this other name and I said, 'OK.'

"We got her in gender therapy and on hormone blockers and she legally changed her name.

"When she was in therapy, the therapist said to me, 'Have you addressed your gender issues?'

"I felt like there was no way I could ever say I was transgender too because otherwise everyone would blame my child's transition on me being trans, so I both appreciated Bub coming out and resented it.

"But the therapist saying it to me sparked a conversation with my wife and I was like, 'I literally hate my body.'"

Spencer said Bub not only inspired him to be his true self, but also claims he wouldn't be alive today if it wasn't for his step-daughter.

He said: "I was suicidal, and I came out as transgender. I wouldn't be here today if I didn't transition.

"Around 13, Bub started going back in the other direction. She was having mental health issues, but she seems pretty comfortable with who she is.

"I like to remind her that she is the reason I'm alive today because if I had not gone through that with her I could not have realised that I am who I am."