A young carer is someone who has to look after parents or siblings who can't always care for themselves because of illness.
The last UK census in 2011 found there were 166,000 young carers in England aged five-17 years.
But new research by BBC News and the University of Nottingham suggests the number could be much higher - possibly up to 800,000 children in England alone.
Read below to find out more about young carers, what they do and what impact it has on them.
Many people don't realise the important and hard role that young carers have in order to help a parent or relative every single day. It can often have an effect on how they live their normal life.
The extra responsibilities that being a carer brings may mean they miss out on school or free time with friends, in order to help their loved one.
Often young carers need to do household jobs too, such as cooking and cleaning, because their parent or guardian is not able to do it themselves.
You wouldn't know if someone is a young carer just by looking at them. Often the work they do as a young carer is going on behind closed doors at home.
Laura Bennett from the charity Carers Trust, which organises Young Carers Day, explains: "Most of you will need to help around the house and support people in your family from time to time.
"This could be things like ironing your school shirt or being extra kind to your brother who is sad because his friend has moved away. This is all part of life being in a family.
"Young carers do more than that - young carers are children and young people under 18 who provide unpaid care to someone in their family who is disabled, physical or mentally ill, and who couldn't manage without their support."
A lot of young carers can be very young. Carers Trust spoke to a group of children aged five to 10 about their caring responsibilities.
It found that almost half of the children it spoke to were having to get up in the night to care for their loved ones, missing out on their own sleep.
One in ten were also having to go to the shops on their own to buy things the family needed.
Many young carers might be what is considered to be 'invisible' or 'hidden'.
This means that official support networks and authorities do not know that they are acting as young carer for someone, which might mean that they are not getting the help that they need.
Some charities are worried that many young carers aren't getting enough support to help them cope.
Some young people might not even realise that they could be a young carer, because they think that what they are doing is a normal part of their day-to-day life.
Anne Longfield, the Children's Commissioner for England, said: "The contribution young carers make to others every day is remarkable. Yet it is still the case that far too many are not even being identified."
If you think that you might be acting as a young carer but not getting the support you need to do this, Laura from Carers Trust has some advice.
"You can talk to someone you trust and ask for their help to get you more support. This could be someone else in your family, or an adult you are close to - maybe an aunt or uncle, or your friend's mum or dad. It could be someone outside of your family like a teacher, doctor or nurse, youth worker, sports coach or faith leader.
"It's okay to say things are difficult, this doesn't mean you are being unfair to the person you care for, or that you or they will get into trouble.
"You are not alone - other children and young people are going through similar things."