You might know some extremely close siblings but we can guarantee they're probably not quite as attached to one another as Anna and Lucy DeCinque. They share a boyfriend and will be talking all about it in the new series of Extreme Sisters:
Anna and Lucy, 35, do pretty much everything together. They wear the same clothes, go to the loo as a pair and even eat the exact same amount of food so that they have identical figures.
The twins, who think of each other as 'one person', even have a similar taste in men. So much so that Anna's boyfriend, Ben, is also Lucy's boyfriend.
The 37-year-old electrician met the siblings on Facebook through a mutual friend and the first night they got together, both sisters kissed him.
Anna and Lucy even say that they'd take their relationship to the next level and marry Ben but Australian law doesn't allow that to happen.
They've also thought about children and decided that, when they do get pregnant, they want to be pregnant with Ben's baby at the exact same time.
If you're already wondering how this works when it comes to bedroom activities, wonder no more because the twins, who live in Perth, Australia said: "How do we say that? Would you say we're a team or... Ben in his own way will please both of us.
"If Ben does something to one twin in the bedroom he has to do it to the other and he already knows that, we don't have to tell him 'Ben what are you doing?'."
They went on to make it very clear that they wouldn't be intimate with each other, adding: "However, we don't do anything with each other, we never have."
Another set of siblings appearing on the show are Brooke and Baylee who are so close that they share the same bed - despite Brooke's husband also being there and not being overly enthusiastic about their set up.
In one scene, the three of them were attempting to come up with a solution. While Brooke's husband was trying to lay down a rule that Baylee was not to get in bed any more, the sisters instead thought it would make more sense for Brooke to sleep in the middle instead of Baylee.
Howard Lee, President of TLC Streaming and Network Originals, said: "Having a close knit family is something most people aspire to and at TLC, we love to explore relationships of all kind.
"In Extreme Sisters, we will introduce sets of inseparable sisters whose bonds are raw, honest and perhaps a little unconventional. Their sibling kinship brings the meaning of sisterhood to a whole other level."
You can watch Extreme Sisters on TLC.