Sisters. They can be a great source of love, support and advice -- but let's face it, sometimes they can also be a giant pain in the butt.
Imagine then, going into business with them.
It's Sisters Day on Sunday, so we asked some of Australia's most successful sister acts working in business together about how they got started, what makes their sister an ideal business partner and who's got whose back.
Daniele and Kaitlyn Wilton
How they got started: Daniele said Smudge Publishing, a boutique culinary travel publisher, was created when she, Kaitlyn and their mum Jonette moved to Victoria's Mornington Peninsula to explore their combined passions of eating, drinking and travelling.
"We got to speak with incredible owners of local wineries and restaurants and asked for their thoughts on publishing a book to showcase the region and its amazing culinary talent," she told The Huffington Post Australia.
"Seven and a half years later, we are living in Melbourne with a team of 20+ spread over Melbourne, Sydney, Brisbane and Adelaide, and 24 books under our belts."
On working with Kaitlyn: "Working with family, and especially your sister, can be very challenging at times but also very rewarding," Daniele said.
"There is no tip-toeing around each other so we get things done pretty quickly. Katie and I have very different personalities; I am one to jump into something head first and Katie is very thoughtful and logical about how we should do things."
Jess and Stef Dadon
How they got started: How Two Live was started as a daily diary in 2012, Jess said.
"Our bold colourful styles and fashion advice received a massive global following, as well as attention from big brands such as ASOS, The Zoe Report, and Maybelline who asked us to work with them," she said.
"We recently published our #howtwolive book which also launches in the US and UK this year, recently launched our TWOOBS shoe range at New York Fashion Week, this summer we're launching a series of events, and getting ready to roll out an initiative which supports women in business."
On working with Stef: "Some people find that working with family can be tough, but if you can make it work then there's no better partnership -- particularly as a sister duo," Jess aid.
"Growing up with the same ideals and values means that even though there are small things we may disagree on, we're always on the same page when it comes to the overall vision and bigger picture.
"We're able to increase efficiency by being completely open and honest."
Juliana Edgell and Gemma Horsfield
How they got started: Smirk Lighting came from Juliana and Gemma's desire to create a better future for their families.
"We believe they should live in a world where there is an abundance of resources for them, their children and their children's children so started Smirk in 2015," the pair told HuffPost Australia.
The company provides energy-efficient lighting solutions for commercial and industrial premises.
"Members of our family have a background in the lighting industry, and this gave us insights into the rapid development of energy efficient products in the market, and the possibilities of intelligent lighting control."
On working together: "The main benefit of working with your sister is that you have a deep understanding of each other, which enables you to read each other quickly, identify each other's attributes and inherently know which areas of the business each would be best at," they said.
Different points of view and ideas about the business have created some "strong" sisterly discussions.
"When we're having a robust debate, we can talk frankly and openly, without any politics at play, as we inherently know that we are striving for the same goal," they said.
Caroline and Melissa Shawyer
How they got started: Melissa said that after pursuing careers in marketing and corporate communications in Australia, Asia and the U.S, the sisters recognised a gap in the market for a PR agency that helped disruptive and growth stage technology businesses tell their story -- and the PR Group was born.
"At that time, media typically focused on the larger players in the sector," she said.
On working with Caroline: "Trust will have to be the single most important benefit," Melissa said. "We are both 100 percent aligned to our vision and trust each other to make the right decisions to deliver to that. I know my sister has my back and I have hers and this is vital when growing a business.
"We won't hesitate to drop the truth on the other if we do not agree with something the other is proposing -- we're passionate about the business we are building."
Berny Bacic and Marie Simunovic
How they got started: Berny said The Burrow Group came from a joint desire to create a connected world through design and merchandise that emotionally bonds brands and people.
"With digital so in the 'now', we wanted to create an agency that specialises on the 'tactile' -- design made for print and beautiful products that you can touch," she said.
On working with Marie: "As sisters, we obviously have similarities, however our strengths lie in different areas," Berny said.
"There is a like-mindedness between the two of us, and we really understand and accept each other's quirks. There is the utmost of trust, comfort and openness that comes when knowing someone forever!
"We never hold back on communicating our thoughts -- whether that be positive or negative!"
Penny Culpo and Maria Nicolaou
How they got started: The Joinery was born after Penny and Maria recognised a lack of dynamic and flexible event and function spaces for hire in Brisbane.
"It's the culmination of our hard work, drive and commitment to the Brisbane hospitality industry over many years, and our family's hard work which has influenced us greatly," Penny said.
"We took over a dilapidated warehouse and commissioned KP Architects to create a cutting edge design landmark to stage some of Brisbane's greatest celebrations and collaborations."
On working with Maria: Penny said running a business with Maria worked because they shared an innate understanding of each other's personalities, values and beliefs.
"We inherently understand each other's vision, are equally invested and have the same amount to lose," she said.
"This transparency and understanding makes day-to-day communication and delivering objectives much more efficient; communication is candid, to say the least!
"We are yin and yang, mutually creating and depending on each other in our combined business ventures."