My parents came from very different families – Dad was an only child from Yorkshire and Mum was one of 10 in an Irish family living in Liverpool. Mum had an awful childhood, which is why she wanted mine and my older brother Jonathan's to be perfect, which put a lot of pressure on us.

We never stayed anywhere longer than three years, including Cyprus and Singapore. Mum and Dad met in Egypt while he was in the army. He was in charge of putting on the entertainment for the forces. Travel was just a natural part of our lives and I didn't know anything different, so it wasn't a matter of having to adapt.

I sort of didn't realise I had an extended family because we moved about so much. My aunt and uncle were also in the army so I was rarely in the same country as them, but my aunt is in her 90s now and is just amazing. She was a midwife during the period of Call the Midwife, so she's been brilliant to talk to. My Irish granny was a pretty hard woman who smoked Player's cigarettes and drank Guinness and she didn't get on with my mum terribly well. She remembers being clipped across the back of the head and asking what she'd done that for and being told, "Well if you haven't done anything naughty, you will soon."

I idolised my brother, who was a toddler when I came along. I'm sure his nose was out of joint when I was born. We were always squabbling. He'd regularly stage mock trials with my teddies and hang them. He's got a very dry sense of humour, whereas I tend to take things quite seriously, so he knew how to wind me up.

Cyprus was the biggest part of my growing up. Mum made us really embrace the local culture wherever we travelled, so we'd go to the local markets, and we had all our clothes made locally too. It was a big culture shock coming back to England to go to boarding school when I was eight. It was wet and green and cold, and I met children who'd lived in the same place all their lives. My school didn't like me going away for work, so I was only let out for really important parts such as The Railway Children.

When I was 16, I left boarding school and we moved to a large modern estate in East Croydon. It was quite strange all being back together. It was a wrench for them to let me go to America when I was 21 to further my career. They wrote me incredibly long letters, which showed me what a loss they felt with me gone.

Cystic fibrosis has played a large part in our family. My parents were both carriers [of the gene], my eldest brother died before I was born and I had a younger sister who never even made it out of the hospital. When my brother's daughter Rachel was born in the late 1970s they were told she wouldn't reach her 10th birthday because of her health complications. I, too, found out I was a carrier when I became pregnant, but luckily my husband's tests came back negative. Thankfully, Rachel has pulled through and is now 35 and healthy.

I was 37 when I married Johan and got pregnant quickly. I'd almost given up on motherhood and thought I'd lost those maternal instincts. My son Jonathan was born five weeks early on Christmas Day 1990. He was very, very tiny and I was incredibly protective but I didn't mollycoddle him.

I'm a grandparent now as my stepdaughter from Johan's previous relationship has two children who are 11 and eight. As a grandparent you are given opportunities to see the world fresh again and are in touch with a whole new world.

• Jenny Agutter is an ambassador for the Cystic Fibrosis Trust, cysticfibrosis.org.uk