Living in a flat opposite your sister means a quick step across the hallway to hang out or just borrow some milk.
Or walk in on one of her underwear models trying on her wares - who also just so happens to be his ex-girlfriend.
Which is exactly what happened to Mark Wright, who stumbled into his sister Jessica's flat not realising that Lucy Mecklenburgh was in there too - and half-naked.
He's behind you! Lucy Mecklenburgh tries on some lingerie and checks herself out in the mirror... as her ex Mark Wright walks in
He stood there smiling at the sexy sight that had greeted him as she grabbed a cushion from the sofa to hide herself.
And he made sure he got a good look at her before he said: 'Oh sh***, this probably ain't the right time.
Wowser! Mark looks stunned - but not disappointed - as Lucy sees him at the door and spins round in surprise
What are you doing here?! Lucy grabs a pillow to cover herself up as Mark walks in
He left immediately and Lucy was left shaking as she told Jessica what had happened.
Mark and Lucy indulged in a short-lived romance at the end of last year which came to an end at Christmas.
You're looking smoking!' That was Mark's parting shot as he smugly eyed up Lucy and left the flat leaving her embarrased
And her new boyfriend Mario has a problem with Mark because of the history with Lucy, and last week he was seen telling her she couldn't go to Jessica's birthday party as Mark would be there.
But this week, Mario came face to face with his love rival as they met in the gym with Mark going over and introducing himself.
I'm shaking: Lucy admitted that the encounter with Mark had left her feeling embarrassed
Mark replied: 'I'm sorry you feel threatened to do with me and Lucy. You don't need to. I was with Lucy ages ago, only seeing her. I stopped seeing her cos I didn't like her anymore.'
The conversation ended with a shake of hands but, as Mark lifted his barbell, Mario couldn't help but throw him a few nasty looks.
Am happy for you: Mark tells Lucy's boyfriend Mario that he has nothing to worry about
But last night, a conversation with his after Mark Snr convinced him to get back out there and start meeting some new women.
It was also the first time that viewers have been introduced to the head of the Wright household as he has avoided being on camera and part of the series until now.
Get out there, son: Viewers met Mark's father, Mark Wright Snr, for the first time last night as he told him to go and meet some girls outside his social circle