A man has sought advice online over his mom trying to break up him and his girlfriend's relationship after they became step-siblings because their parents married.

The family problems were revealed in a Reddit post earlier this month where the 20-year-old man wanted others to help him with the difficult situation.

'My girlfriend and I were childhood friends turned high school/college sweethearts,' the man wrote at the beginning of his post.

Crazy: A 20-year-old male started dating his girlfriend when they were 14 years old. After their relationship started, his mother and her father started dating (stock picture)

'We are both 20 now and have been dating since we were 14,' he continued.

His mom and his girlfriend's dad, who are both divorced from their previous partners, started dating after their children were already together and the parents recently married each other.

'Weirdly enough, while they were just dating they were totally fine with my girlfriend and I being together, but it pretty much changed immediately when they got married last year and moved in together,' the man wrote.

Problem arose after the wedding when his mom started to refer to his girlfriend as his 'sister', which lead the man to believe the parents are trying to split them up despite their six-year-long relationship.

He wrote: 'I think she is doing it on purpose to get under my skin.'

The couple currently lives in the household with the parents because the man's father and the woman's mother are not an option to help them. They both go to a state college and can not afford to pay rent at this time.

'Our parents have become laser focused on breaking us up, calling us brother and sister at every opportunity and lecturing us about how disgusting it is, asking us aren't we embarrassed that our friends know, saying that it's not anyone's fault that they got married first and this is just the way it has to be,' the post continued.

'I love this girl and have spent my life with her. I want to spend the rest of my life with her. I just can't stomach breaking up when we are fine and it is this bizarre outside circumstance trying to drive a wedge between us.'

Our parents have become laser focused on breaking us up

The man wanted to know if it was 'inapppopriate no matter what to date your "stepsister" who you live with' in his Reddit post.

Commenters appeared to be on the side of the boyfriend and girlfriend because their relationship started prior to their parents dating.

'You and your girlfriend have been together far longer than your parents,' one commenter wrote.

'Your parents are ones who are making it weird. If anything, your friends probably think it's weird that your parents got married and are trying to break the two of you up after six years.'

Other people advised for the couple to make their parents uncomfortable in a similar way to prove how terrible they are making the situation.

'Since your parents are being so demeaning and gross, especially when you and your gf got together, I would definitely just take it up a notch,' another commenter advised.